INFLUENCE OF A SINGLE INGAAS QUANTUM-WELL ON CURRENT TRANSPORT AND DEEP LEVELS IN GAAS

An comprehensive study of the effects of tunneling on the I-V characte ristics and the deep level trap spectroscopy was conducted on GaAs/Inx Ga1-xAs/GaAs single quantum wells (SQWs) with different indium composi tion (x = 0.15, 0.24) and well width (t(w) = 80, 200 Angstrom) by temp erature-varying current-voltage characteristics (I-V-T), deep level tr ansient spectroscopy (DLTS) and photoreflectance (PR) spectroscopy. By the correlated analyses, we found that the tunneling emissions have o bvious effects on the I-V characteristics and the DLTS spectra. The I- V-T measurements revealed clear effects of SQWs on the overall current flow. Thermionic field emission (TFE) was observed at low temperature and low voltage bias regions. The magnitude of the current of the sam ples with thinner quantum well width was found to be higher than that with thicker well width because of the higher tunneling probability of electrons from the SQWs. The DLTS spectra showed a typical plateau-li ke feature which was attributed to the tunneling emission from the InG aAs quantum well. A hole trap, H1, with activation energy Delta E(a) = 0.52-0.56 eV was also observed for ail samples. We relate this hole t rap to the gallium vacancies in the GaAs bulk. The photoreflectance sp ectra showed an obvious absorption feature which corresponds to the tr ansitions in the InxGa1-xAs SQWs.