DLTS and photoluminescence of MBE GaAs grown in the presence of hydrogen

Abstract

We report here electrical transport, deep level transient spectroscopy (DLTS) and low-temperature photoluminescence (PL) studies aimed at investigating the effect of hydrogen on deep and shallow levels in Sn doped GaAs, prepared by solid source MBE, in the presence of a 1 10 -6 Torr hydrogen back-pressure. Electrical transport and PL data show that the use of hydrogen results in a significant decrease of the unintentional shallow donor and acceptor concentration. As a result, high electron mobility (84200 cm 2/V·s at 77 K) and high PL quality GaAs could be prepared. The M1, M3, and M4 deep electron trap concentrations were found to decrease by one order of magnitude in layers grown at either 580 and 640°C, in the presence of hydrogen. The deep level concentration of samples grown at 640°C with hydrogen are in the low 10 11 cm -3 range. The effect of hydrogen may be due either to the incorporation of shallow and deep levels at a reduced rate or to their passivation. Different tentative explanations are suggested, which, to some extent, can be supported by literature dealing with post-growth hydrogenation treatments of crystalline GaAs and of clean GaAs surfaces.