Capacitance-voltage profiling and thermal evolution of the conduction band-offset of unstrained Ga0.47In0.53As/InP single quantum well

We report the results of capacitance-voltage (C-V) and Deep Level Transient Spectroscopy (DLTS) measurements performed upon a Ga0.47In0.53As/InP quant um well structure. At room temperature, a conduction-band offset Delta E-c = (200+/-10)meV and charge densities sigma(1) = +/-(3+/-1)*10(11) times the electronic charge per cm(2) have been measured from C-V experiments. At lo wer temperature (T less than or equal to 150K) we have observed an importan t decrease of the band-offset, considerably larger than a pure thermal effe ct. We have shown that the explanation lies in the presence of a high conce ntration of deep traps located at the well-barrier interfaces. Two species A and B have been detected through DLTS experiments with activation energie s E-tA = 90 meV and E-tB = 195 meV, respectively. The filling of these trap levels at low temperature lowers the band offset from 200 to 120 meV, owin g to band repulsion effects.