Admittance spectroscopy and thermal stimulation current for band-offset characteristics in AlAs/GaAs n(+)-p structures

Admittance spectroscopy is used to study a molecular-beam epitaxially grown GaAs n(+)-p diode with 100-Angstrom-thick AlAs immersed in the lightly dop ed p-region. The measurements clearly show two trapping effects. Upon compa rison with the reference sample without the AlAs layer, an equivalent circu it for the studied sample is developed. Based on this circuit, the admittan ce spectra are calculated and found to be consistent with the experimental spectra. From this result, the trap at E-a = 0.52 eV with a capture cross s ection 1.6 x 10(-14) cm(2) is believed to result from the resistance-capaci tance time constant effect due to the thermionic emission of holes over the AlAs barrier and the activation energy corresponds to the AlAs/GaAs valenc e-band offset. The results of the thermal stimulation current further suppo rt this conclusion.