Light-emitting heterostructures with single and multiple GaAs/InGaAs quantum wells have been investigated by means of electrochemical capacitance-voltage (ECV) profiling. Capacitance-voltage characteristics were measured; concentration profiles of free charge carriers over the heterostructure depth as well as the intensity of quantum well filling by charge carriers were obtained. In heterostructures with a single quantum well (QW) we considered limitations of capacitance techniques for undoped QW profiling, which is situated near the metallurgic border of the p−n-junction. We made a detailed consideration of phenomena related to Debye smearing and we developed and analyzed the dependence of the space charge region width on the doping. Special attention was paid to investigation of the "blind" area. This was inspired by the practical problem from capacitance spectroscopy of semiconductors, when the researcher poses the task of obtaining a free charge carrier depth distribution profile as deep as possible in the space charge region, i.e. where the intensity of the electric field is maximum. Generally, the active QW of a LED heterostructure is placed deep in the space charge region, so reaching these regions is extremely important for practical problems. We present an evolution of capacitance-voltage characteristics during ECV profiling of nonuniformly doped p − n− heterostructures. For a heterostructure with multiple quantum wells we registered a response from 6 QWs.
The capability of plasma‐enhanced atomic layer deposition (PE‐ALD) for the formation of GaP nucleation layers on Si substrates for further epitaxial growth is explored. The possibility of epitaxial growth of GaP by metalorganic vapor phase epitaxy (MOVPE) on templates prepared by PE‐ALD GaP/Si is demonstrated. The structural and electronic properties of the interfaces between the GaP nucleation layer and the Si substrate as well as their thermal stability are studied. Initially, the GaP/Si structures obtained by PE‐ALD without additional hydrogen plasma exhibit better photoelectric properties compared with that fabricated with high H2 plasma power that induces the formation of defects in the silicon subsurface layer. Annealing at temperatures of 550–600 °C leads to a decrease in the defect concentration created by the hydrogen plasma. Thus, after annealing, the GaP/Si interfaces fabricated by both types of PE‐ALD processes exhibit similar quality. Thermal treatment of the GaP/Si structures at temperatures of 725–750 °C leads to the diffusion of phosphorus from GaP into Si and to the formation of an isotype n‐GaP/n–p‐Si heterojunction with improved photoelectric properties. High‐temperature stability of the GaP/Si interface fabricated by PE‐ALD is essential for its prospective use for GaP/Si templates.
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