PROTON IMPLANTATION-INDUCED DAMAGE TO HEAVILY-DOPED N-GAAS AS ENVISAGED BY CHARGE DEEP-LEVEL TRANSIENT SPECTROSCOPY

Heavily doped (1 to 3 x 10(18) cm(-3)) GaAs:Si wafers were exposed to high doses (10(14), 10(15) cm(-2)) of 150 keV protons. When applying t he lower dose, the related charge DLTS spectra a of Al/GaAs diodes com prise a peak of dielectric relaxation (DR) and a trap-limited peak (MG ) due to the emission from a midgap level. The former peak can be attr ibuted to a linear Debye-type polarization connected with a hopping tr ansport of electrons within the damaged region. If taking samples from different positions on the original wafer, the position of tile DR pe ak on the temperature axis T-m for a selected rate window has been fou nd to vary when passing from one sample to another, a shift toward hig her temperature has been accompanied by a corresponding increase in th e activation energy (0.1 to 0.22 eV). The MG level emission rate is qu ite sensitive to the electric field intensity in the semiconductor, as manifested by shifting T-m to lower temperatures via higher reverse b iases. By contrast, the ultimate dose of 10(15) protons/cm(2) introduc ed defect levels at 0.07 and 0.31 eV below E-c, respectively, a result that can be reconciled with previous reports relevant to lower doses. Concluding, tile DR peak occurrence may be considered as a criterion for a successful GaAs isolation after tile impact of protons, tile opt imum dose lying closely to the 10(14) cm(-2) level.