Proper interpretation of photoconductive decay transients in semiconductors having finite surface recombination velocity

Abstract

The influence of finite surface recombination velocity on the proper interpretation of photoconductive decay (PCD) transients in semiconductors is discussed. The limitations of simple analytical equations which relate the observed effective lifetime to the material parameters are considered. It is shown that, under most circumstances, the correct application of the appropriate analytical expression requires some prior knowledge of the material parameters under investigation. Several methods are proposed to extract useful information from PCD experiments. Finally, the practicality of these methods is investigated by measuring the effective lifetimes of high-purity germanium and float-zone silicon using a noncontact PCD technique.

Determination of surface recombination velocity and bulk lifetime in detector grade silicon and germanium crystals

“…Figure Sa shows 1/7:~ffvs. l/L using the experimental data and the fit obtained by modeling the exact solutions to the equation governing the decay of the photoexcited carriers in Si [8]. The parameters used in the fitting curve were: 'rB =2500~, D =28 cm 2 /sec.…”

Interplay Between Strain and Thickness on the Effective Carrier Lifetime of Buffer-Mediated Epitaxial Germanium Probed by the Photoconductance Decay Technique

“…In the limits of effectively small epilayer thickness, d , and when the condition of S ≪ 2D/ d is satisfied, τ S ≈ 2 S / d and eq can be rewritten as , where D is the minority carrier diffusion coefficient under low injection and d is the length of the epilayer (thickness) along the growth direction. The factor of 2 in eq stems from the symmetric treatment of the top and bottom interfaces in ref , in contrast with the asymmetric treatment in other noted works. , From eq , it can be propounded that when 1/τ eff is plotted against 2/ d recorded over samples of varied thicknesses, d , τ bulk and S can be quantified from the y -intercept and slope, respectively, provided that the surface conditions remain unaltered.…”

“…In the limits of effectively small epilayer thickness, d, and when the condition of S ≪ 2D/d is satisfied, τ S ≈ 2S/d and eq 2 can be rewritten as 44,45 = + S d…”