THERMALLY STIMULATED CURRENT SPECTROSCOPY ON SILICON PLANAR-DOPED GAAS SAMPLES

Using thermally stimulated current (TSC) spectroscopy we have identifi ed the presence of several deep traps in low temperature grown (LTG) n onintentionally doped bulk molecular beam epitaxy (MBE)-GaAs and silic on planar-doped MBE-GaAs samples. The experiments of TSC spectroscopy were carried out on a LTG MBE-GaAs epilayer grown at 300 degrees C and the planar-doped layer with a nominal silicon concentration of 3.4 X 10(12) cm(-2). The LTG nonintentionally doped bulk MBE-GaAs sample sho ws three peaks in the TSC spectra but the planar-doped MBE-GaAs sample shows spectra similar to those of bulk samples grown by the liquid-en capsulated Czochralski and vertical gradient freeze methods. The main achievement is the experimental evidence that the potential well prese nt in the planar-doped sample is effective in detecting the presence o f different deep traps previously not seen in LTG bulk MBE-GaAs epilay ers due to a shorter carrier lifetime (about 10(-12) s) in the conduct ion band which occurs due to EL2-like deep traps recombination. This f act is evidenced by a strong hopping conduction in LTG bulk MBE-GaAs s amples at temperatures lower than 300 K, but not in planar-doped MBE-G aAs samples because the two-dimensional electron gas has a higher mobi lity than lateral LTG bulk MBE-GaAs epilayers. (C) 1998 American Insti tute of Physics. [S0021-8979(98)09016-1]