Minority-carrier lifetimes and internal quantum efficiency of surface-free GaAs

Abstract

Minority‐carrier lifetimes, internal quantum efficiencies, and values of the radiative recombination coefficient B are determined from photoluminescence time‐decay and external quantum efficiency data taken for LPE GaAs samples (germanium doped or undoped) in the doping range 1.9×10¹⁵?p₀ ?1×10¹⁹ cm⁻³ at 300 °K. Measurements are made on isotype double heterostructure samples where the optically exicted GaAs layer is bounded by wider‐band‐gap Ga_0.5Al_0.5As layers which provide for confinement of minority carriers and also minimize the importance of surface or interfacial recombination on the measured lifetimes. Comparison with time‐decay data for samples without the ternary cladding layers shows the dominant effect of surface and substrate recombination on the decay time if confinement layers are not provided. Luminescence decay times are observed from 1.2 nsec for heavily doped samples up to 1.3 μsec for lightly doped samples. Values of the bulk minority‐carrier lifetimes, radiative lifetimes, and internal quantum efficiencies are determined. The experimental values for B agree well with existing theory for heavily doped material. For lightly doped material, the experimental B coefficient is larger than expected from the single‐electron model.