Studies on excimer laser doping of GaAs using sulphur adsorbate as dopant source

Abstract

Excimer laser doping of GaAs using sulphur adsorbate as a dopant source is demonstrated. Box-like n-type layers of depths of about 100 nm with carrier concentration as high as (2∼3)×1019 cm−3 are formed. Passivation of GaAs using a (NH4)2Sx solution for 40 min followed by sublimation of the excess sulphur atoms in high vacuum result in an effective dopant for controllable n-type doping. The samples are irradiated using a KrF excimer laser in a N2 gaseous environment. Secondary ion mass spectrometry (SIMS) measurements show that sulphur is successfully incorporated in the GaAs. The sheet resistance is controlled by adjusting the laser energy fluence and number of laser pulses. Rutherford backscattering spectrometry with channeling (RBS/C) alignment measurement indicates that lattice damage is undetectable for N2 gas pressures of 760 Torr.