Lifetime and diffusion length inhomogeneity controlled by point and extended defect interaction in n-GaAs LEC

The role of native defect inhomogeneity on the minority-carrier properties in n-type GaAs LEC has been investigated. An array of Au/GaAs Schottky diodes has been evaporated along the wafer diameter; then the net donor concentration and the hole diffusion length were measured by C-V and SPV methods, respectively. The distribution of extended defects was measured by etch pit observations and electron beam induced current (EBIC) imaging. In order to correlate diffusion length and recombination centre radial distribution, a deep level transient spectroscopy (DLTS) investigation was carried out. A W-shaped distribution of etch pit density ranging from 2 X 10(4) to 1 X 10(5) cm-2 was found, while an M-shaped diffusion length within the interval (0.7-2.3) X 10(-4) cm was observed. The lifetime tau of the minority carriers has been directly measured by the photocurrent decay method and a value ranging in the interval (5-10) X 10(-9) s was found. Some hypotheses on the dominant trap controlling the diffusion length and the lifetime and on its interaction with dislocations are discussed. The inhomogeneous distribution of the transport properties has been explained on the basis of different point-extended defects interaction in differently dislocated regions