Growth of strained GaAs 1 y Sb y and GaAs 1 y z Sb y N z quantum wells on InP substrates

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1 Journal of Crystal Growth 310 (2008) Growth of strained GaAs 1 y Sb y and GaAs 1 y z Sb y N z quantum wells on InP substrates J.Y.T. Huang a,, D.P. Xu a, X. Song c, S.E. Babcock c, T.F. Kuech b, L.J. Mawst a a Department of Electrical and Computer Engineering, University of Wisconsin-Madison, 1415 Engineering Drive, Madison, WI , USA b Department of Chemical and Biological Engineering, University of Wisconsin-Madison, 1415 Engineering Drive, Madison, WI , USA c Department of Material Science and Engineering, University of Wisconsin-Madison, 1415 Engineering Drive, Madison, WI , USA Available online 15 January 2008 Abstract The metal organic vapor-phase epitaxy (MOVPE) growth conditions and properties of fully strained GaAs 1 y z Sb y N z /InP multiquantum wells (MQWs) are investigated. Higher Sb incorporation within the strained GaAs 1 y Sb y layers was observed when using a higher Sb/(As+Sb) precursor ratio and higher growth temperature. However, lattice-latching effects and the strain values ultimately limit the maximum amount of Sb incorporated. In GaAs 1 y z Sb y N z layers, a decrease of AsH 3 precursor flux leads to an increase of N and Sb incorporation, whereas an increase of unsymmetrical dimethylhydrazine (U-DMHy) precursor flux leads to an increase of N and a decrease of Sb incorporation. The photoluminescence emission from the GaAs 1 y z Sb y N z QW is observed to red-shift with decreasing AsH 3 and increasing U-DMHy flux. Sb accumulation at the InP to GaAs 1 y z Sb y N z interface is also observed from secondary ion mass spectroscopy analysis, indicating further optimization of switching sequences is required to improve the compositional uniformity of the QW. r 2007 Elsevier B.V. All rights reserved. PACS: De; Cr; Gh Keywords: A3. Metal organic chemical vapor deposition; A3. Quantum wells; B1. Antimonides; B1. Nitrides; B2. Semiconducting III V materials; B2. Semiconducting indium phosphide 1. Introduction The dilute-nitride GaAs 1 y z Sb y N z /InP material system is a narrow band gap alloy with potential for microelectronic and optoelectronic device applications. The GaAs 1 y Sb y /InP heterojunction forms a staggered type-ii band lineup with a narrow band gap in the GaAs 1 y Sb y, which is promising for application to solar cells, high-speed double heterojunction bipolar transistors, laser diodes, and photodetectors. Incorporation of a dilute amount of nitrogen offers simultaneously a reduction of the band gap energy and the lattice constant. GaAs 1 y z Sb y N z /GaAs quantum wells (QWs) emit light at room temperature and have been demonstrated in the mm wavelength range by molecular beam epitaxy (MBE) [1] and at 1.3 mm Corresponding author. Tel.: ; fax: address: yuting@cae.wisc.edu (J.Y.T. Huang). wavelength by metal organic vapor-phase epitaxy (MOVPE) [2]. The value of the band gap energy is reduced further in the GaAs 1 y z Sb y N z /GaAs system compared with the InGaAsN/GaAs system for a given nitrogen concentration [3 5]. Therefore, GaAs 1 y z Sb y N z is an important alternative material to InGaAsN for long wavelength emission. Due to material strain and difficulties in achieving high, controlled, nitrogen incorporation, dilute-nitride materials must be developed on InP or GaSb substrates in order to access the mid-wave infrared MWIR. Photodetectors and emitters using such III V materials on an InP substrate would be highly desirable, since well-established processing technologies could then be employed. The advantages of InP over GaSb as a substrate material include a higher thermal conductivity, the ability to utilize buried heterostructure designs for current confinement and lateral heat removal, and incorporation of the device layers into vertical cavity surface emitting lasers /$ - see front matter r 2007 Elsevier B.V. All rights reserved. doi: /j.jcrysgro

2 J.Y.T. Huang et al. / Journal of Crystal Growth 310 (2008) Highly strained InGaAs active regions on InP encounter difficulties for wavelengths beyond 2 mm [6]. A design study of a dilute-nitride In(Ga)AsN/GaAs 1 y Sb y type-ii W QW structure on an InP substrate for emission in the 2 5 mm range was proposed [7]. However, the MOVPEbased growth of these materials remains quite challenging because of the observed reduction in N incorporation into InGaAs(N) alloys at high indium compositions [8 10]. Recently, InP-based GaAs 1 y z Sb y N z /GaAs 1 y Sb y type-ii QW structures have been investigated for light emission over the 2 3 mm wavelength region through the MOVPE growth technique [11]. Few published studies exist on the growth of strained GaAs 1 y Sb y QWs on InP substrates [12]. Almost all previous studies have been performed on bulk GaAsSb alloys. The growth of low defect density, homogenous GaAs 1 y Sb y /InP layers remains challenging. Thermodynamics predicts the phase separation of GaAs 1 y Sb y into two binary materials below the critical temperature (T c ), with a mixture of GaAs and GaSb existing over a wide alloy composition range corresponding to the GaAs 1 y Sb y miscibility gap (0.2oSbo0.8) for strain-relaxed materials [14]. The use of strained materials can alter the phase relationships, and thermodynamically stable compositions can be achieved particularly near lattice-matched conditions [15]. Strained GaAs 1 y Sb y does exhibit stable compositions, both in theory [15] and in practice [16,17]. The use of non-equilibrium growth techniques such as MBE and MOVPE can also assist in the development of materials that are not thermodynamically favored due to the kinetic limitations to the transport and chemical processes that allow the system to relax to the equilibrium phase distribution. In the MOVPE growth environment, the low vapor pressure of antimony, the tendency toward Sb-atoms segregation/memory effects at heterointerfaces containing GaAsSb alloys [18,19] can lead to the formation of GaP-rich, InAs-rich, and GaSb-rich compounds [20] at the heterointerfaces. For example, the formation of an InPSb interface layer has been reported and tentatively explained by a thermodynamic model of strain-induced surface melting of thin layers [21]. These interfacial layers can lead to undesirable and somewhat uncontrolled changes of the band offsets and radiative efficiency [22] resulting in severe degradation of type-ii laser performance and gain in HBTs [23]. At the GaAs 1 y Sb y /InP interface, both the group III and V layer constituents change further complicating the formation of a compositionally abrupt interface. While GaAs 1 y z Sb y N z compounds have been grown previously on GaAs substrates [1,2], a study on the growth conditions and characteristics of strained GaAs 1 y z Sb y N z multiple quantum wells (MQWs) on InP substrates is presented in this paper [13]. 2. Experimental procedure The MOVPE growth of strained GaAs 1 y z Sb y N z /InP heterostructures on nominally exact (1 0 0) InP substrates was carried out at growth temperatures in the range of C with a reactor pressure of 100 mbar and hydrogen as the carrier gas. Trimethylgallium (TMGa) was the group III precursor; PH 3, AsH 3, trimethylantimony (TMSb), and unsymmetrical dimethylhydrazine (U-DMHy) were the group V precursors. An optimized gas-switching sequence was used to achieve abrupt interfaces with minimum compositional grading between the alternating layers. At the InP-to-GaAs 1 y Sb y interface, prior to turning on TMSb, AsH 3 was applied for a duration of 2 s followed by 5 s of interruption with both TMSb and AsH 3 before the growth of the GaAs 1 y Sb y layer. This switching sequence establishes the presence of the antimony precursor prior to the introduction of TMGa, i.e., the onset of GaAs 1 y Sb y layer growth. For all GaAs 1 y z Sb y N z layers, the molar flow rate of TMGa and TMSb during the growth is and mol/min, respectively. The same TMSb molar flow rate was used during the pre-purge. The TMSb prepurge procedure is used to improve Sb incorporation into the grown material and reduce the compositional grading at the interface [24]. At the GaAs 1 y Sb y -to- InP interface, all group V supplies were immediately terminated after the GaAs 1 y Sb y layer growth, while maintaining the TMGa flow for 1 s. Following the 1 s TMGa flow, a low AsH 3 flow was introduced for 5 s. The gas-switching of the 1 s TMGa purge is to utilize the group- III metal to collect the Sb atoms on top of the epitaxial surface. The 5-period GaAs 1 y Sb y /InP MQW structures were grown on un-doped semi-insulating (1 0 0) InP substrates by MOVPE. Prior to the growth of the MQWs, a 1 mm thick InP buffer layer was grown. The growth rates for GaAs 1 y Sb y and InP MQW were 0.14 and 0.21 nm/s, respectively. The V/III ratio varies from 4.3 to 7.3 and high gas-phase Sb-precursor fractions (Sb/V ratio) ranging from 0.57 to 0.97 were employed for the GaAs 1 y Sb y layers. All growth parameters were kept fixed for all samples except for variations of the AsH 3 flow rate. The solid phase material composition of GaAs 1 y z Sb y N z layers was determined by the combined use of high-resolution X-ray diffraction (HRXRD), cross-sectional transmission electron microscope (TEM), electron microprobe analysis (EMPA), and secondary ion mass spectroscopy (SIMS). The XRD spectra were fitted by a dynamical simulation model (Philips X Pert Eptaxy) for HRXRD on-axis (0 0 4) o 2y scans and also characterized through off-axis (1 1 5) reciprocal space mapping (RSM) to estimate the strain state, layer thickness, and the composition of the GaAs 1 y Sb y layers. The photoluminescence (PL) was measured at 30 K, with excitation by an argon laser (l514.5 nm) and detection by a liquidnitrogen-cooled Ge and InSb photodiode. All the PL data were obtained by 2 nm per scan step, indicating 1 nm accuracy for the PL peak wavelength. All measurements were performed on as-grown samples that had not been thermally annealed.

3 2384 ARTICLE IN PRESS J.Y.T. Huang et al. / Journal of Crystal Growth 310 (2008) Results and discussions 3.1. Effect of growth conditions At the growth temperature (T g ) of 550 1C, the Sb mole fractions of the strained GaAs 1 y Sb y QW layers were within the range of y ¼ and increased with an increase of Sb/V precursor ratio. Fig. 1(a) shows that the solid-phase concentration of Sb in the GaAs 1 y Sb y layer increases proportionally with increasing vapor-phase composition ([TMSb]/([AsH 3 ]+[TMSb]). The highest and lowest ends of the compositional range could be limited by either strain relaxation or lattice-latching effects [19,25]; therefore, the Sb increment with increasing Sb/V precursor ratio is not significant at the high- and low-end of the Sb-content ranges in the GaAs 1 y Sb y layers. TEM measurements were performed on selected samples to determine the layer thickness and substantiate the HRXRD estimates of the composition. The layer thickness of GaAs 1 y Sb y and InP were estimated to be in the range of and nm, respectively, from TEM analysis. The ratio of the GaAs 1 y Sb y thickness to the InP thicknesses can be estimated from the TEM images with a thickness error of 70.3 nm. Since the period of the superlattice (SL) is also accurately known from HRXRD, the individual layer thicknesses can then be determined. The upper- and lower-bound thicknesses were then utilized in the dynamical XRD simulations to estimate the Sb composition. Based on the thickness error bars, we can estimate the antimony compositional accuracy as y=70.01 using XRD dynamical simulation. Fig. 1(b) presents the HRXRD spectrum for the Sb compositions as indicated. The discrepancy between the HRXRD spectrum and simulation could be a result of a non-ideal interface due to the formation of a graded composition transitional layer, such as an Sb-rich or Asrich heterointerface. Simulation studies including thin interfacial layers of InPSb, which is possible based on our gas-switching sequence, were found to lead to minimal changes in Sb concentration and GaAs 1 y Sb y thickness, i.e. within the range of the error shown in Fig. 1(b). However, we found it is difficult to improve the fit between simulation and experiment using a transitional interface layer. Fig. 2 shows the asymmetric RSM recorded around the (1 1 5) reflection which provides information of the strain relaxation. The RSM for the SL structures at the highest and lowest Sb concentrations are shown in Fig. 2(a) and (b); the effects of growth temperature (T g ) on Sb concentration at the temperature of 550 and 490 1C are shown in Fig. 2(b) and (c), respectively. The RSM from these samples indicates that the SL satellite spectral peaks exhibit sharp, well-defined features. Also, there are no major diffraction peaks in the in-plane direction away from the (1 1 5) InP peak, and the SL satellite peaks and the center of the InP reciprocal lattice point are aligned on a straight line parallel to the Q y orientation. Therefore, all Solid Phase Sb-mole Fraction (y in GaAs 1-y Sb y ) Sb composition 30K PL Gas Phase TMSb/ (AsH 3 +TMSb) ratio Log Intensity (a.u.) (i) (ii) ω (degree) GaAsSb/InP MQWs were grown coherently strained on the InP layers Effect of growth temperature Sb diffusion into InP is strongly enhanced at temperatures in excess of 550 1C and above during MOVPE growth 30K PL Peak Wavelength (nm) y = 0.36 ± 0.01 y = 0.65 ± 0.01 Fig. 1. (a) Solid phase Sb composition (solid diamond) and 30 K PL peak wavelength (open square) versus gas-phase Sb/V ratio. The solid curves are provided as a guide to the eye. All samples consist of five period GaAs 1 y Sb y (4 6 nm)/inp (26 28 nm) MQWs grown at 550 1C and at a constant [TMSb]/[TMGa] precursor ratio of (b) The (0 0 4) o/2y scans of GaAs 1 y Sb y /InP MQWs for different Sb compositions as indicated in the figure (upper profiles: measurements; lower profiles: simulations). The simulation results presented here are (i) GaAs Sb (5.14 nm)/inp (26.16 nm) and (ii) GaAs Sb (4.50 nm)/inp (22.40 nm).

4 J.Y.T. Huang et al. / Journal of Crystal Growth 310 (2008) Q y (rlu) Fig. 2. (1 1 5) RSM of 5-period of strained superlattice structures: (a) sample A: 550 1C, Sb/V ¼ 0.567; (b) sample B: 550 1C, Sb/V ¼ 0.968; (c) sample C: 490 1C, Sb/V ¼ All samples were grown with a constant growth time of both GaAs 1 y Sb y and InP layers. The unit rlu is defined as l/2d, where the X-ray wavelength l is nm. Q x (rlu) [18], thus it is important to optimize the growth temperature, T g, to limit compositional grading at the interface. Fig. 3(a) presents the (0 0 4) HRXRD diffraction spectra for samples consisting of strained GaAs 1 y Sb y /InP MQWs as T g is varied from 480 to 550 1C under constant precursor ratios of As/Ga and Sb/Ga of and 4.142, respectively. Sharp X-ray spectra with many satellite peaks are observed indicating little change in structural quality and minimal compositional changes over the growth temperature range studied. The HRXRD spectra do shift slightly with growth temperature due to slight changes in both the Sb concentration and layer thickness. The Arrhenius plot in Fig. 3(b) shows the effect of the growth temperature on the Sb mole fraction and the growth rate in the strained GaAs 1 y Sb y layers. Both the Sb mole fraction and growth rate increase with increasing growth temperature. The decomposition rates of TMGa and TMSb can result in changes in the growth rate and material properties with substrate temperature variations. Based on HRXRD analysis, the growth rate increases from 8.5 to 11.8 nm/min with increasing i g from 480 to 550 1C due to these temperature sensitive reaction rates. TMSb has a reported 50% pyrolysis rate at a temperature of around 550 1C, and homogeneous arsine pyrolysis is 50% complete at 600 1C [26]. These reactions, particularly at the lower growth temperatures, are heterogeneous, and there is a competition for the available adsorption and decomposition sites at the surface between the various anion species. Although both AsH 3 and TMSb decomposition increase with increasing temperature, AsH 3 adsorption, reaction and incorporation on available Ga surface sites would be favored over Sb [16]. A higher growth rate can enhance the Sb incorporation rate through kinetic trapping of species on the surface [16]. The balance between these competing effects can lead to the general increase of Sb with increasing temperature GaAs 1 y z Sb y N z /InP multiple quantum wells GaAs 1 y z Sb y N z alloys are expected to have material issues similar to other dilute-nitride alloys such as InGaAsN and GaAsN. The significant degradation of the electron mobility and the PL efficiency, the broadening of the spectral PL FWHM, and potential N clustering are expected, due to the impurity-like nature of N compared with III V alloys anions, such as As, P, and Sb. The 5-period GaAs 1 y z Sb y N z /InP MQWs studied here were grown at a fixed growth temperature of 550 1C. Constant TMGa and TMSb gas-phase mole fractions and variable AsH 3 and U-DMHy gas-phase mole fractions were employed in the growth of the GaAs 1 y z Sb y (N z ) layers. A series of samples were grown to determine the influence of AsH 3 (A C) and U-DMHy (D I) growth conditions on material properties (Table 1). In this series of samples, all the growth conditions were held constant for samples A, B, and C (Table 1) except for the AsH 3 gas-phase mole fraction. Previous reports indicated that an increase of In incorporation leads to a decrease of N incorporation in InGaAsN [27,28] and an increase of Sb incorporation leads to a decrease of N

5 2386 ARTICLE IN PRESS J.Y.T. Huang et al. / Journal of Crystal Growth 310 (2008) y in GaAs 1-y Sb y Log Intensity (a.u.) C 520 C 490 C 480 C ω/2θ (arc seconds) Temperature ( C) /T (K -1 ) Fig. 3. (a) HRXRD spectra of the (0 0 4) o/2y scans of GaAs 1 y Sby/InP SLs for different growth temperatures as indicated in the figure (upper profiles: measurements; lower profiles: simulations). The simulation results showed as follows: T g ¼ 550 1C, GaAs Sb (5.53 nm)/inp (22.18 nm); T g ¼ 520 1C, GaAs Sb (5.40 nm)/inp (20.89 nm); T g ¼ 490 1C, GaAs Sb (4.08 nm)/inp (22.60 nm); T g ¼ 480 1C, GaAs Sb (3.96 nm)/inp (22.63 nm). All samples were grown at a constant Sb/V ratio of and a constant growth time of both GaAs 1 y Sb y and InP layers. (b) Arrhenius 19 plot of Sb mole fraction and growth rate derived from (a) as a function of inverse growth temperature. incorporation in GaAs 1 y z Sb y N z [29] when grown on a GaAs substrate. Note that it is not possible to uniquely determine the N content using HRXRD for the quaternary material. Selected samples were also analyzed using EPMA, however large uncertainty occurs in determining the N content of these dilute-nitride materials. From EMPA, the N mole fraction increases from to and the Sb mole fraction increases from to as the AsH 3 /V ratio is decreased, which is in agreement with Ref. [29] for GaAs 1 y z Sb y (N z ) on GaAs substrate. In Fig. 4, as the AsH 3 gas-phase mole fraction decreases, the 30 K PL peak emission wavelength increases from 1380 to 1590 nm due to the reduction of the band gap energy from the combined increase in the Sb and N concentration. The ln (Growth Rate) (nm/min) PL intensity decreases with increasing emission wavelength (Fig. 4(b)), presumably a result of increased N content and is indicative of increased non-radiative recombination. As in other dilute-nitride material systems [1,2,30 32], an improvement of the PL intensity could perhaps be achieved through thermal annealing. The influence of the U-DMHy gas-phase mole fraction was investigated wherein all the growth conditions for two sets of samples, D G and H I, were held constant, as indicated in Table 1, except for the U-DMHy mole fraction. s D G have a higher AsH 3 flux compared with samples H I. With increasing U-DMHy flux, the nitrogen incorporation increases and the corresponding Sb content decreases for samples D G and H I under constant As and Sb precursor fluxes. For samples E G, EMPA does not indicate the nitrogen value, presumably due to the large uncertainty in the N concentrations measured using EMPA, as discussed above. However, the red-shift in emission wavelength and decrease in PL intensity indicates that nitrogen is indeed incorporated. In addition, we observe that the growth rate increases with increasing U-DMHy flux, as determined from the SL period from HRXRD measurements. In Fig. 5, the 30 K PL spectra for these samples shift from 1456 to 1480 nm with the increase in the N/V precursor ratio, accompanied by a broadening of the PL FWHM and a decrease in the PL intensity. From both Figs. 4(a) and 5(a), a very low AsH 3 gasphase mole fraction is needed to achieve the higher rates of Sb and N incorporation. The growth rate is found to increase with the U-DMHy mole fraction (Fig. 5(a)), whereas it is insensitive to the AsH 3 mole fraction (Fig. 4(a)). The growth of the GaAs 1 y z Sb y N z layer may require a critical Sb surface coverage, similar to that observed for GaAs 1 y Sb y [19]. Before reaching the critical Sb surface coverage, an initial interface layer may also be formed. When increasing the TMSb partial pressure, by employing lower U-DMHy flux in Fig. 5(a), the thickness of the initial layer decreases due to the rapid build-up of the critical Sb concentration. A similar effect was observed that an increase of Sb at the surface of GaAs 1 y Sb y on GaAs leads to a decrease of the growth rate in the kinetically limited growth regime [24]. Therefore, lower U-DMHy flux leads to a thinner GaAs 1 y z Sb y N z layer. On the other hand, in Fig. 4(a), due to a very low AsH 3 partial pressure, the surface is saturated with the decomposition of TMGa, TMSb, and U-DMHy; the growth rate is insensitive to the AsH 3 flux. The dependence of U-DMHy flow was also characterized by SIMS in Fig. 6 with the same AsH 3, TMGa, and TMSb flow in samples D G. The U-DMHy/V precursor ratios are 0.971, 0.985, 0.989, from the substrate up. Each GaAs 1 y z Sb y N z layer 5 nm is sandwiched between 37.5 nm of InP. The lack of a known N-content SIMS calibration sample prevents absolute determination of the nitrogen concentration. The nitrogen incorporation increases with increasing U-DMHy flux but saturates at high

6 J.Y.T. Huang et al. / Journal of Crystal Growth 310 (2008) Table 1 Effect of precursor flow conditions on Sb mole fraction (y) and N mole fraction (z) in the strained GaAs 1 y z Sb y N z /InP SLs AsH 3 (mol/min) U-DMHy (mol/min) As/V ratio N/V ratio GaAs 1 y z Sb y N z (from EMPA) Thickness one period of SL (nm) y z A 3.43E E B 1.72E E C 1.09E E D 1.72E E 1.72E E F 1.72E E G 1.72E E H 1.09E I 1.09E E The molar flow rates of TMGa and TMSb were fixed at and mol/min, respectively. The selected samples were characterized by EMPA, and the SL period thickness was determined by HRXRD. All samples were grown with a constant growth time of both GaAs 1 y Sb y (N z ) and InP layers at a growth temperature of 550 1C and a reactor pressure of 100 mbar. Growth Rate (nm/min) FWHM (nm) Wavelength (nm) C B AsH 3 /V precursor ratio A Growth Rate (nm/min) FWHM (nm) Wavelength (nm) E F G U-DMHy/V precirsor ratio 80 A 30 K 80 E 30 K PL intensity (a.u.) B x 5 C x 15 PL intensity (a.u.) F G Wavelength (nm) Wavelength (nm) Fig. 4. s A, B, and C. (a) Variation in the growth rate in strained GaAs 1 y z Sb y N z layers, 30 K PL peak wavelength, and full width at half maximum (FWHM) as a function of AsH 3 /V precursor ratio. (b) Illustration of 30 K PL spectra. Fig. 5. s E, F, and G. (a) Variation in the growth rate in strained GaAs 1 y z Sb y N z layers, 30 K PL peak wavelength, and full width at half maximum (FWHM) as a function of U-DMHy/V precursor ratio. (b) Illustration of 30 K PL spectra.

7 2388 ARTICLE IN PRESS J.Y.T. Huang et al. / Journal of Crystal Growth 310 (2008) Acknowledgments N Intensity (Arb. unit) flux. At a low U-DMHy/V ratio of 0.971, due to the lower N concentration and the depth resolution limit of SIMS, the N signal is barely detected. An asymmetry in the Sb concentration is clearly observed in Fig. 6, where the dashed lines represent the positions of the GaAsSbN QWs and the Sb profiles are shifted toward the lower GaAsSbN/ InP interface. This interface is formed as an Sb-rich layer, such as InPSb in the GaAsSb/InP system, and its concentration is found to be independent of U-DMHy flux. It is possible that the gas-switching sequence of applying TMSb pre-purge procedure leads to the observed increase in Sb incorporation at the lower GaAsSbN/InP interface. 4. Conclusions DMHy/V precursor ratios: 0.991, 0.989, 0.985,0.971 Ga Sb Depth (nm) Fig. 6. SIMS profiles of GaAs 1 y z Sb y N z (6 nm)/inp (37.5 nm) grown using various U-DMHy flux. The dashed lines are a guide to the eye for the heterointerfaces. The MOVPE growth conditions and properties of fully strained GaAs 1 y z Sb y N z /InP MQWs have been studied. These materials are attractive for achieving mid-ir emission by implementing GaAs 1 y z Sb y N z /GaAs 1 y Sb y / InP type-ii QWs. Higher Sb incorporation rates in the strained GaAs 1 y Sb y layers were observed at higher Sb/ (As+Sb) precursor ratios and higher growth temperatures. In GaAs 1 y z Sb y N z layers, a decrease of AsH 3 precursor flux is found to lead to an increase of N and Sb incorporation, whereas an increase of U-DMHy precursor flux results in an increase of N and a decrease of Sb incorporation. Furthermore, we observe red-shifted PL emission and reduction in PL intensity in GaAs 1 y z Sb y N z, presumably a result of increased N and Sb incorporation, with decreasing AsH 3. An accumulation of Sb is also observed at the lower GaAsSbN/InP interface by SIMS. 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