Evidence of strong effect from the interface on the electrical characteristics of ZnSe/GaAs heterojunctions

Abstract

The interface properties of ZnSe/GaAs heterojunctions grown by molecular beam epitaxy have been studied by electrical methods. The current-voltage and capacitance-voltage characteristics show a hysteresis which can be related to unusually slow current and capacitance transients in response to a change in the reverse bias. We performed admittance spectroscopy measurements at various frequencies in order to investigate this phenomenon. A large frequency dispersion of the capacitance and a broad peak in conductance spectra suggest the presence of interface states at the heterojunction between ZnSe and GaAs. We ascribe the long transients to slow changes in the charge on these interface states. We also propose that interface states result in a voltage-induced lowering of the barrier at the heterointerface. The capacitance versus frequency data were analyzed in terms of Lehovec's model from which the density of interface states of 3 -4ϫ10 12 cm Ϫ2 eV Ϫ1 were calculated.

Surface photovoltage spectroscopy of pulsed laser deposited undoped ZnSe/n+GaAs

“…The induced ac voltage on the TCG with respect to the grounded copper sample holder was measured using a buffer circuit and lock-in amplifier (EG&G model 7260). The buffer circuit had a very high input impedance (∼10 12 ) so that the voltages measured are unaffected by the high input impedance of the MIS structure used in our measurements. The actual value of the SPV signal was obtained by calibrating the voltage on the TCG using a standard voltage source.…”

“…In a previous publication, we have shown that pulsed laser deposition technique gives rise to good epitaxial quality ZnSe layers [10]. The ZnSe/GaAs heterointerface is associated with many properties different from homointerfaces, which have been studied by electrical and optical techniques [11,12]. In this paper, we present the details of the SPS results of the ZnSe/GaAs heterojunctions in order to understand the nature of the ZnSe epilayer and heterointerface.…”

Effect of hydrostatic pressure on degradation of CdTe/CdMgTe heterostructures grown by molecular beam epitaxy on GaAs substrates

“…These strains are relaxed by formation of structural defects like stacking faults and dislocations. Existing stacking faults and other defects near the interface, like the case of ZnSe grown on GaAs [1][2][3][4][5][6][7] are frequently the sources of new dislocations which propagate from the interface into the epitaxial epilayer [19] sometimes leading to internal micro-cracks.…”

“…Several reports on ZnSe-based heterostructures have shown that formation of structural defects at the ZnSe/GaAs interface plays a crucial role in the degradation process [1][2][3][4][5][6][7]. Strains induced by the lattice mismatch between the substrate and the epilayer lead to creation of many crystal defects (point defects, dislocations, V-shape stacking faults etc) near the interface.…”

“…One of them was studied after pressure application (step three), the second was not subjected to pressure (step one). 4 …”