Effects of carrier confinement by InGaAs/GaAs heterointerface barrier on deep trap concentration profiling

Carrier confinement by the conduction-band barrier formed by the band discontinuity Delta E/sub c/ has been observed in molecular beam epitaxy (MBE)-grown In/sub 0.1/Ga/sub 0.9/As/GaAs heterostructures as evidenced by the decrease of DLTS (deep level transient spectroscopy) peak height with increased filling pulse amplitude in a fixed-reverse-bias variable-filling-pulse DLTS study. A DLTS model including the Delta E/sub c/ effects on trap profiling is developed by considering conduction-band barrier as a giant deep trap with an electron emission rate depending exponentially on Delta E/sub c/. The model explains quantitatively the experimental observations of the effects of Delta E/sub c/ in the DLTS study and shows that an erroneous trap concentration profile may result from the conduction-band barrier if the standard DLTS model is used. It is shown that a 0.16-eV+or-0.01-eV electron trap reported to be located only at the heterointerface of In/sub 0.53/Ga/sub 0.47/As/InP may actually be a deep-trap characteristic of InGaAs with a fairly uniform trap concentration throughout the InGaAs epilayer.<
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