Nondestructive evaluation of junction effects in GaAs avalanche photoconductors

We have studied the current-voltage-temperature response of off-state NIN GaAs Avalanche Photoconductors. These non-destructive tests, evaluated in terms of thermal activation energies (E a ), and Resistance-Voltage (R-V) characteristics, are found to effectively distinguish between two types of devices. The first type possesses E a gap /2 and resistivity commensurate with bulk SI GaAs; the second demonstrates E a > E gap /s and R values greatly surpassing those of bulk Semi-Insulating GaAs. These data are consistent with junction effects at both contact-bulk interfaces, arising from the formation of an uncompensated P-type region near the N + contact layer. We explain the P-type behavior by trapped electron neutralization of the deep compensating donor EL2.