By quantitative secondary ion mass spectroscopy (SIMS) analyses, oxygen and carbon contents in GaAs epitaxial layers grown by molecular beam epitaxy (MBE) were found to increase significantly when the growth temperature was reduced below a critical value at about 450 °C. The concentrations of oxygen and carbon in GaAs epilayers grown below the critical temperature were about 4×1017 cm−3 and 3×1016 cm−3, respectively. Meanwhile, impurity accumulation during growth interruption became faster resulting in even higher interfacial impurity concentrations. Oxygen and carbon will affect the electrical properties of the GaAs epilayers, especially those grown between 350 °C and 450 °C where defects related to excess As may not be dominating.

An improved zero-bias thermally stimulated current (TSC) technique was successfully applied to characterize the traps in semi-insulating gallium arsenide buffer layers grown at low temperature by molecular beam epitaxy (MBE) for the reduction of backgating in gallium arsenide based integrated circuits. Conventional TSC technique is not suitable because of the strong leakage current in those buffer layers. Special precaution is needed to suppress the leakage current even when the bias is nominally zero. An electron trap with an activation energy of 0.52 eV was found in annealed buffer layers. In addition, a continuum of states, which were attributed to the interface states at the interface of arsenic precipitates and bulk gallium arsenide, was also detected.

Despite many separate studies of the two dominant defects, i.e., As precipitates and arsenic-antisite (AsGa)-related traps, in GaAs epilayers grown by molecular beam epitaxy at low temperatures, they are seldom examined simultaneously. In this letter, we report the detection of both defects in electron trap spectrum obtained by zero quiescent bias voltage transient current spectroscopy. The As precipitates appear as a broad continuum of states in the lower temperature region (<280 K) of the spectra whereas the AsGa-related defect appears as a discrete peak at a higher temperature. The AsGa-related trap has an activation energy of 0.65 eV and a capture cross section of 9.3×10−14 cm2. It is found that the trap characteristic of low temperature GaAs is strongly dependent on its growth temperature and the above mentioned defects may not dominate in some cases.

Previously, Lau [W. S. Law: Jpn. J. Appl. Phys. 29 (1990) L690] has pointed out that part of the hysteresis ΔV + in MNS (Metal-Nitride-Silicon) capacitors is correlated to the spin density measured by electron spin resonance and the other part of the hysteresis ΔV - is correlated to defects close to the nitride/silicon interface. The spin density was thought to originate from silicon dangling bonds in the silicon nitride. 254 nm ultraviolet irradiation, which was known to be capable of producing silicon dangling bonds in silicon nitride, was found to induce a large ΔV + in nearly hysteresis free MNS (Metal-Nitride-Silicon) capacitors, thus confirming that ΔV + is correlated to silicon dangling bonds.

Electron traps in undoped-GaAs epitaxial layers grown at low temperatures (<300 °C) by molecular beam epitaxy were studied by the zero-bias thermally stimulated current technique. Four traps T1-4 were detected in as-grown samples. It was also found that all the traps detected can be annealed out except the T1 trap. However, the buffer layer, with or without annealing, was found to be an effective remedy for backgating in high electron mobility transistors, indicating that the T1 trap may have a much more significant role than the three shallower traps in the suppression of backgating. The T1 trap is believed to be the EL3 electron trap which is related to oxygen contamination.