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 ΔE_c has been observed in molecular beam epitaxy (MBE)-grown In_0.1Ga_0.9As/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 ΔE_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 ΔE_c. The model explains quantitatively the experimental observations of the effects of ΔE_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±0.01-eV electron trap reported to be located only at the heterointerface of In_0.53Ga_0.47As/InP may actually be a deep-trap characteristic of InGaAs with a fairly uniform trap concentration throughout the InGaAs epilayer