substance: cadmium selenide (CdSe) 26s11d30 property: hole mobility, carrier and ion diffusion hole Hall mobility hole drift mobility

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1 substance: cadmium selenide (CdSe) property: hole mobility, carrier and ion diffusion Hall and drift mobilities of holes are smaller than those of electrons. hole Hall mobility (in cm 2 /Vs) 26s11d30 µ H,p 40 T = 300 K cubic CdSe/(100)GaAs, N-doped epitaxial 94O films, free-hole concentration cm 3 50 T = 300 K pulsed field effect 69I T = 300 K Hall effect 74B 10 T = 300 K Hall effect 75P 0.5 T = 300 K ion implanted layers, Hall effect 78K hole drift mobility (in cm 2 /Vs) µ dr,p 75 T = 300 K time of flight measurement 72C T = 300 K high resistivity samples, time of flight 75P measurement 20 T = 300 K electron beam excited pulses 77P Dependence on electric field: Fig. 1 hole diffusion coefficient D p 65 cm 2 /s T = 13 K nonlinear transient gratings 78J D p 0.52 cm 2 /s T = 300 K surface diffusion constant, surface 85S photovoltage measurements on films exciton diffusion coefficient (in cm 2 /s) Exciton diffusion coefficients vs temperature, see Fig. 2. A review on exciton diffusion in CdSe in comparison with CdS and Cd(S,Se) has been published by [92S]. D 140 T = 2 K transient-grating measurements 93E 26 T = 30 K D 20 T = 2 K transient-grating measurements 93E 6.6 T = 30 K D x 2.5 T = 4.5 K transient-grating measurements, 92P 3.6 T = 30 K excitation below A n=2 exciton 20 T = 1.8 K transient-grating measurements, 92S 6 T = 40 K excitation below A n=1 exciton carrier diffusion lengths L [µm] n [cm 3 ] τ [ns]* T [K] remarks 13(7) (1) 5 electron-hole plasma expansion, local 85M PL intensity and gain spectra minority-carrier diffusion, theory 87M 0.09? 80 hole diffusion length, estimated from 85P photoresponse measurements on hex-cdse heterostructures on n-gap ? 300 electrodeposited films on Ti substrates 87S after different postdeposition treatments * τ carrier lifetime

2 exciton diffusion lengths Exciton diffusion length vs temperature, see Fig. 3. L x [µm] n [cm 3 ] T [K] remarks ? 80 hex-cdse heterostructures on n-gap 85P carrier diffusion velocity (in 10 6 cm/s) Given T are bath temperatures υ sr T = 300 K surface recombination velocity, from 85S surface photovoltage measurements on films υ ct 0.4 carrier transfer velocity at surface υ p = υ sr + υ ct true carrier velocity at surface/interface carrier ambipolar diffusion velocity (in 10 6 cm/s) υ D 3 T = 5 K drift-υ D electron-hole plasma expansion, 85M local PL intensity and gain spectra 19 T = 4.2 K expansion velocity of the plasma-exciton 90S boundary, time-resolved absorption ion and defect diffusion and migration Self-diffusion of constituent ions Cd 2+ is described by the formula D = D 0 exp(-q/k B T). Fig. 4 gives D as function of temperature. D cm 2 /s T variable Auger spectroscopy 91F Q 1.73 ev E(Se sublimation ) 1.2(1) ev T variable Se desorption experiments 98O

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4 Fig. 1. CdSe. Electron and hole drift velocity of 2 different samples vs. electric field strength at room temperature [72C].

5 Fig. 2. CdSe, hex. Exciton diffusion coefficients parallel and perpendicular to the c axis vs temperature. Solid curves are to guide the eye. The inset shows the ratio D /D [93E].

6 Fig. 3. CdSe, hex. Diffusion length L x of excitons vs temperature. The solid curve is to guide the eye [93E].

7 Fig. 4. CdSe, hex. Temperature dependence of the self-diffusion coefficient of Cd ions [91F].