The method of scanning Kelvin-probe microscopy is used to show that the effect of triboelectrification is observed when the tip of an atomic-force microscope interacts with the surface of n-GaAs epitaxial layers. The sign of the change in the potential indicates that the sample surface after triboelectrification becomes more negative. The observed specific features of the phenomena can be attributed to the thermally activated generation of point defects in the vicinity of the sample surface due to deformation caused by the tip.

The differential capacitance and differential active conductance of rectifying contacts of n -GaN and n -In x Ga 1 − x N ( x ≈ 0.15) with an electrolyte (0.2 M aqueous solutions of NaOH, NaCl, or HCl) have been studied. It was found that electron states with energies corresponding to the upper half of the energy gap of a semiconductor exist at the interface between these semiconductors and a NaOH solution. The density and characteristic recharging time of states noticeably contributing to the differential capacitance and differential active conductance at probe-voltage frequencies of 0.3–1 kHz grow with their binding energy and, for states lying at 0.15–0.3 eV below the conduction-band bottom of n -GaN, fall within the ranges 10 12 –2 × 10 13 cm −2 eV −1 and 10 −4 –10 −2 s, respectively. For contacts with NaCl and HCl solutions, there are no states of this kind. It is assumed that the observed states are related to the adsorption of hydroxyl groups.

An estimation carried out via scanning Kelvin probe microscopy (SKPM) confirms that valleys on the initial surface of n-type InN layers correspond to a decrease in electrostatic potential by at least several millivolts. At the same time, surfaces subjected to anodic oxidization (the oxide thickness is no less than 10 nm) do not support this correspondence in remarkable number of cases. This is apparently caused by fluctuations in the oxide’s charge. Strong oxidization is found to lead to a substantial increase in the energy of the conduction-band bottom on the InN surface. The average potential of an oxidized surface is demonstrated to exceed that of the initial one and be positive with respect to the SKPM probe. The measured data enable us to infer that the electron work function of InN anodic oxide is less than 5 eV.

The depth distribution of free carriers over the HEMT structures with quantum-well layers is studied by electrochemical capacitance-voltage profiling. It is shown that the actual distribution of the concentration of free carriers and their energy spectrum in the HEMT structure channel can be obtained by numerical simulation of the results of profiling based on the self-consistent solution of one-dimensional Schrödinger and Poisson equations.

Dependences of differential capacitance of the system degenerate n -InN-electrolyte on the voltage are measured at a frequency of the probing voltage of 300 Hz. Qualitative analysis of these characteristics is performed based on a one-dimensional model of the metal-insulator-semiconductor structure in the region of bias voltages near the flat-band voltage and depletion. It is shown that the magnitude of capacitance in this voltage region is affected by electron states at the interface. The density and energy distribution of these states are evaluated. The form of the voltage dependence of capacitance in the region of accumulation also indicates the existence of the states at the interface, the energy of which exceeds the energy of the conduction band bottom by several tenths of eV. The density of these states increases as the energy increases.

Dependences of differential capacitance of the electrolyte-n-InN (0001) contact on the bias voltage are studied. Their analysis of the basis of a model similar to a model of the MIS structure shows that the energy spectrum of surface states of InN above the conduction band bottom can be represented by two, relatively narrow, bands of deep levels described by the Gaussian distribution. Parameters of these bands are as follows: the average energy counted from the conduction band bottom, ΔE 1 ≈ 0.15 eV and ΔE 2 ≈ 0.9 eV; and the mean-square deviation, ΔE 1 ≈ 0.15–0.25 eV and ΔE 2 ≈ 0.05–0.1 eV. The total density of states in the bands are (1–2.5) × 1012 and (0.2–4) × 1012 cm–2.

The exact solution of the Thomas–Fermi equation for a planar accumulation layer of a degenerate semiconductor is presented. The obtained results are compared with theoretical literature data. The applicability of the solution is demonstrated by using results of electrochemical capacitance–voltage measurements and photoluminescence data for n‐InN epilayers. It has been found that the difference between the electron concentrations estimated from the Hall and photoluminescence measurements is a measure of the electron content in the accumulation layer with acceptable accuracy. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)