Optical Deep-Level Transient Conductance Characterisation of Semi-Insulating Gallium Arsenide Treated with Hydrogen Plasma

Abstract

Optical deep-level transient conductance spectroscopy (ODLTCS) has been employed to characterise Schottky devices fabricated on liquid encapsulation Czochralski (LEC) semi-insulating (SI) GaAs material which has been exposed to low-pressure microwave (2.42 GHz) H2 plasma. A range of substrate temperatures and exposure times to the plasma were tested. An increase in device conductance spectra amplitudes were observed after 60 min of H2 plasma treatment at 100° C, 300° C, and 400° C. In devices exposed to H2 plasma at 200° C, the conductance spectra decreased in magnitude with time and after 60 min and 120 min treatments, the spectra were identical to that of the control device. The change in device conductance under the above conditions suggests that there is (i) an optimal plasma condition for the passivation of defects by atomic H with the formation of neutral defect-H (DH) complexes, (ii) the reaction between defects and atomic H is time dependent, and (iii) the LEC SI GaAs materials are contaminated with H during the growth process. In contrast, the increase in magnitude of ODLTC spectrum after 200° C treatment with molecular H for 60 min confirms the role of passivation by the atomic H.