Towards Solid State Photomultiplier

Transcription

1 Towards Solid State Photomultiplier High Speed Avalanche Photodiodes QD based Photodiodes Dr Chee Hing Tan ( 陳志興 ) Reader in Optoelectronic Sensors

2 Contents Introduction Basics of avalanche photodiodes Electron-APD and nm scale avalanche regions High speed avalanche photodiodes Quantum dot based photodiodes.

3 Introduction

4 The Department of Electronic and Electrical Engineering

5 The University of Sheffield Origins date back to Firth College (1879) + Sheffield Technical School (1884) + Sheffield School of Medicine (1828) University College of Sheffield in 1897 University of Sheffield granted Charter in 1905

6 Overview of EEE department (Top 5) ~31 members academic staff ~50 research staff Student community comprises ~500 undergraduate and postgraduate taught and research students Research and teaching activities are spread across 3 research groups Communications Electrical Machines & Drives Semiconductor Materials & Devices

7 EPSRC National Centre for III-V Technologies Epitaxial Growth Capabilities MOVPE Ga,In,Al,As,P MOVPE Ga,In,Al,As,(P) MOVPE Ga,In,Al,N MBE 1 Ga,In,Al As.P,N MBE 2 Ga,In,Al As,Sb, Bi

8 Low noise APDs High speed APDs CHT Chee Hing Tan Jo Shien Ng John Paul David MWIR and LWIR JPD&CHT Novel avalanche materials JPD & JSN Single photon X-ray, UV JSN, CHT & JPD

9 Physics of avalanche photodiodes

10 PMT and MCP 200nm-1700nm 4-25 m PMT High gain Fast response 3/8 to 20 Sensitive to vibration, magnetic field, temperature Higher cost MCP High gain Fast response Immune to magnetic fields and vibration Lower power consumption Compact High cost D* >1x10 15 cmhz 1/2 /W but not suitable for imaging arrays

11 Holes and electrons ii Significant gain fluctuation Stochastic, Significant noise and limited bandwidth M=1 absorption avalanche Impact ionisation Electrons (holes) only ii Minimal gain fluctuation Deterministic, Low noise and high bandwidth M=24 absorption avalanche p drift avalanche n h absorption avalanche M=24 M=6 absorption avalanche M=24 absorption avalanche M=24 absorption avalanche Current (A) 10-2 Photocurrent Dark current Geiger mode Reverse bias (V)

12 Gain Gain vs. Reverse bias is a reasonable indicator of k = / value M exp( w) Gain and excess noise for k=0 and k=1 M 1 1 w Reverse bias (V) Excess noise vs. Gain is a very good indicator of k value Excess noise factor F F Measured Ideal shot Gain noise noise km ( 2 1/ M)(1 k) F M F 2 1/ M

13 Current technologies Excess noise factor Increasing k k =0, 0.1, 1.0 InGaAs/InP ( m) -Mature IR APDs/SPADs -Poor performance relative to Si Si ( m) -Excellent, mature and affordable APDs/SPADs Cd x Hg 1-x Te( m) -Excellent IR APDs -Limited availability Gain To achieve a solid state PMT, k=0 is the most promising approach CdHgTe (or CMT) APD is the leading technology. What next??????

14 Single photon detection J.Beck et al., IEEE LEOS Newsletter, Oct Baker et al. SPIE Vol D imaging, SPAD with raster scan,buller et al. Heriot-Watt

15 Research: Can InAs work as a Solid State PMT???

16 InAs electron-apds InAs (ev) Cd 0.3 Hg 0.7 Te (ev) E g (ev) E GX (ev) 1.39 (3.91E g ) 3.18 (10.97E g ) E GL (ev) 0.98(2.8E g ) 1.97(6.79E g ) Cd 0.3 Hg 0.7 Te

17 Initial challenges in InAs Almost no prior work due to preconceptions Unavoidable surface leakage High background doping High tunnelling current Leakage current (A) 1e-2 1e-3 1e-4 1e-5 atom concentration (cm -3 ) 1e+21 1e+20 1e+19 1e+18 1e+17 1e+16 1e+15 SIMs for InAs12 Si Be As Al 1e+6 1e+5 1e+4 1e+3 1e+2 1e+1 count (/s) 1e-6 Reverse leakage current density (A/cm 2 ) Reverse voltage (V) 200 m radius 100 m radius Tunnelling Multiplied tunnelling W=1 m Reverse bias voltage (V) Reverse leakage current density (A/cm 2 ) e m radius 25 m radius Tunnelling Multiplied tunnelling W=2 m distance ( m) Reverse bias voltage (V) 1e+0

18 Dark current Bulk Current Density (A/cm 2 ) E A =0.36eV E A =0.18eV proportional to n i 2 J surface proportional to n i J bulk Experimental background limited data /T (K -1 ) Bulk at high T Surface leakage at low T Surface Current per unit length (A/cm) Total reverse current (A) Reverse Bias Voltage (V) Dark current for 110µmdiameter SU-8 passivated APD 77K 100K 125K 150K 175K 200K 220K 250K 290K

19 Responsivity / leakage current comparison in pin Detectivity (cmhz 1/2 /W) /T (K -1 ) Calculated detectivity Judson InAs Hamamatsu InAs High Detectivity InAs PD, Ready to move towards Solid State PMT Current density (A/cm 2 ) Responsivity (A/W) Sheffield InAs 300K Sheffield InAs 77K Judson InAs Hamamatsu InAs Wavelength ( m) Sheffield InAs Hamamatsu InAs Judson InAs Reverse voltage (V)

20 InAs electron-apds m 2 m 1 m Gain p Reverse Bias Voltage (V) i n M V vs M (75um cap A) V vs M (50um cap A) V vs M (50um cap A) Multiplication n i p V Reverse bias voltage (V) No measurable hole impact ionisation, confirming electron only avalanche process

21 Avalanche Noise Excess Noise Factor, F InAs AlInAs CMT (SWIR) Multiplication, M CMT data from Beck et al. Proc. SPIE Vol. 5564, p AlInAs data from Goh et al. Journal of Quantum Electronics Excess noise factor, F Multiplication factor, M F is independent of temperature VISION: InAs single photon avalanche photodiode for visible to SWIR wavelengths up to 3 m

22 SWIR Geiger mode Arrays/FPAs Current (A) Princeton Lightwave: 32x32 GmAPD camera Photocurrent Dark current Reverse bias (V) FLIR (Core by Indigo) but low bias < 5V but InGaAs/InP works at >20V Rothman et. al, Detectors for Astronomy Workshop 2009 VISION: Work towards low voltage APD FPA (Solid State PMT FPA??)

23 InAs electron-apds Bandwidth limited by the transit time, not the avalanche process. This means unlimited gainbandwidth product. 5 3dB bandwidth (GHz) GHz Gain-bandwidth product Multiplication factor InAs low noise high APDs for free space communication (>40 Gb/s) and LIDAR at m 1

24 InAs X-ray APDs Fano limited energy resolution Improved FWHM for X-ray detection

25 I n t e n s i t y ( c p s ) InAsBi at Sheffield X R D s p e c tra o f In A s B i o n In A s 107 S T B 0 H 3 S T B 0 H 5 S T B 0 H 6 * [ B i] = 4. 2 % 103 [ B i] = 1. 7 % 102 [ B i] = 0. 4 % O M E G A _ 2 T H E T A ( a r c se c ) -42 mev/% Bi for InAsSb -46 mev/% Bi for InAsSbBi -55 mev/% Bi for InAsBi Bi based IR e-apds?

26 Exploring the nonlocal effects in nm scale avalanche region for Solid State PMT 5 nm 50 nm 500 nm 1 m

27 Avalanche statistics at high field SMC E=600kV/cm 600kV/cm 800 p(x,t) 2.5e e e e e e e e+19 number of ii events kV/cm 300kV/cm 1.0e e e-7 2.0e-7 1.5e-7 1.0e-7 x(m) Monte Carlo simulation in GaAs 5.0e e-12 2e-12 3e-12 p(x,t) 5e-12 4e-12 t(s) 2.5e e e e e e-6 2.5e-6 SMC E=300kV/cm kV/cm 0 1e+17 2e+17 3e+17 3e e-6 1.5e-6 x(m) 1.0e-6 5.0e x/w 0 1e-11 2e-11 3e-11 5e-11 4e-11 t(s)

28 Excess noise in thin avalanche regions Excess Noise Factor, F GaAs w = 1 m w = 0.5 m w = 0.3 m w = 0.2 m w = 0.1 m w = m k=0.2 Excess noise factor, F InP k=2.4 Fujitsu SAM APD decreasing w k=1 k=0.4 Excess Noise Factor, F blue: M e red:m mix Si k=1 k=0.5 k=0.3 k= Multiplication, M e 1 10 Multiplication, M k= Multiplication, M Excess noise corresponds to k~ when w <100 nm. Even smaller w is required to reduce excess noise towards unity. Is wide bandgap materials the answer?

29 6 Al 0.6 Ga 0.4 As Excess noise in wide bandgap materials Al 0.8 Ga 0.2 As excess noise factor, F e k=0.1 F h (0.1 m n + -i-p + ) F e (0.1 m p + -i-n + ) F e (0.05 m p + -i-n + ) F e (0.025 m p + -i-n + ) 2 F e (26nm) multiplication factor, M e Noise comparable to Si when w = 25 nm in wide indirect bandgap materials (similar trends for x= 0.7 and 0.9)

30 F (M~10) Novel AlAsSb APDs 5.0 InP Avalanche Width (mm) InAlAs Excess Noise Factor AlAsSb APD Hamamatsu Si APD Fujitsu InGaAs/InP APD Gain 200nm AlAsSb has extremely low noise Can we achieve even lower noise using thinner avalanche region?

31 Extremely low temperature coefficient of breakdown voltage 30 Measured current (A) Reverse bias (V) C bd (mv/k) Material w (nm) C bd (mv/k) w (nm) C bd (mv/k) AlAsSb Si GaAs Al 0.6 Ga 0.4 As GaInP InP InAlAs Avalanche region thickness ( m)

32 High speed avalanche photodiodes

33 Current materials for 1.55 m APDs Gain_bandwidth Product (GHz) InAlAs APDs InAlAs APDs Sheffield InP APDs Ge on Si APD Year InAlAs and InP have reached their limits??? InAs requires very small area and have some issues with surface leakage. Waveguide APD with gain ~3 works at 40Gb/s.

34 APD design M= Drift time absorption Avalanche multiplication M=10 >200GHz >1THz >500GHz GBP (GHz) Bandwidth (GHz) Avalanche region thickness(nm) GBP1_20nm GBP2_40nm GBP3_60nm GBP4_80nm GBP5_100nm GBP6_150nm GBP7_200nm GBP0_no absorption BW1_20nm BW2_40nm BW3_60nm BW4_80nm BW5_100nm BW6_150nm BW7_200nm BW0_no absorption Absorption width(nm) GHz W m <100nm W a <1000n m 500GHz W m <45nm W a <500nm Multiplication thickness (nm) 1THz W m <20nm W a <100nm For bandwidth >100GHz w a <150 and w m <20 nm

35 Wide band APDs 1000 Absolute impedance w ridge p i n w p w gap d Zt Zb Ci Zm Gl Lm Impedance ( ) L=15 L=30 L= Frequency (GHz) 2 Bias= 17.0 V Relative response (db) L = 30 m L = 55 m XPDV diode Frequency (GHz)

36 Wide band APDs Response (dbm) Absorption =1200nm 2D Graph v vs Col 3 17V vs Col v vs Col 13 18V vs Col v vs Col 23 19V vs Col v vs Col 33 20v vs Col 38 22V vs Col 43 24v vs Col 48 26V vs Col 53 28V vs Col 58 30V vs Col 63 31V vs Col 68 32V vs Col 73 33V vs Col 78 Noise floor vs Col 82 Response (dbm) /04/ Frequency (GHz) Frequency (GHz) 24.8 V 24 V 23.6 V 23 V 22 V 21 V 20 V 19.5 V 19 V 18.5 V 18 V Noise floor XPDV diode Absorption =400nm 36

37 QD detectors for imaging: How to achieve low cost and multifunction?? 1550 o C o C

38 QD on Si for low cost FPA UoSHEFF UCL QDIP on Silicon is promising!

39 VISION: Reconfigurable IR sensors Can be dynamically configured into High resolution multicolour FPA Multispectral : Row-by-row Multispectral : Full FPA Future Intelligent Sensors? No moving parts Multispectral: Pixel-by-pixel No cooled optical filters needed

40 Algorithmic spectrometer 20nm ( m) Optimised Algorithim ( m) Quantum Dot Infrared Photodiodes (QDIPs) ( m) MWIR LWIR

41 Multicolor using a single detector 1.0 Responsivity (A/W) Projection algorithm Wavelength ( m) Multispectral imaging without dispersive optics? Responsivity (A/W) Wavelength ( m)

42 Spectroscopy without dispersive optics?? Power per unit Area (W/m 2 ) Power on Device Theoretical Reconstruction um FWHM Power per unit Area (W/m 2 ) Power on Device Algorithm Reconstruction um FWHM Algorithm Reconstruction - 0.5um FWHM Wavelength ( m) Wavelength ( m) Vines et al. Versatile spectral imaging with an algorithmbased spectrometer using highly tuneable quantum dot infrared photodetectors. IEEE Journal of Quantum Electronics, 47(2), Absorption feature as small as 300nm measured

43 Thank you

44 To Discover And Understand.

45 Seeing photons: Progress and Limits of Visible and Infrared Sensor Arrays ( p.62 ultralarge-format arrays; mosaic tiling technologies; pixel size reduction; smarter pixels and on-focal plane processing; improved threedimensional (3-D) integration and hybridization; higher-operating-temperature devices; multicolor pixels; improved short-wavelength infrared (SWIR) arrays; photon counting technologies and lower readout noise; curved focal surfaces; lower-power operation; radiation hardening; cost reduction; and improved cooler technology. 24/04/

46 Novel Applications 120 o C 24/04/

47 Detectivity Bulk semiconductors InSb, InAs, HgCdTe Conduction band Valence band Detectivity = Responsivity x Area 0.5 Noise current Impurity doped semiconductors Ge:Zn, Si:As Conduction band Impurity band Conduction band Impurity band Bulk is the leading technology in terms of D* What next???? Valence band Valence band 24/04/

48 LWIR photodetector comparison A Rogalski

49 Photonic Bandgap 49 h p i n 24/04/2012

50 Photonic Bandgap 50 Posani et al., APL 88,151104,2006 J. Rosenberg, physics.optics,16july2009 VISION: Multispectral and polarimetric sensing 24/04/2012

51 BULK N and Bi detectors 51 InAsN InAsBi 24/04/2012

52 MWIR Type II InAs/GaSb 52 EMRSDTC Room temperature Type II FPA on GaAs 24/04/2012

53 InGaAs InGaAs has large / at low fields. What about InAs???