In electroreflectance (ER) using the semiconductor-electrolyte technique (saturated solution, 0.5 N, of NH4NO3 in ethyl alcohol at T ∼ 300 °K), a method of modulation of the surface barrier by single-sign square-wave pulses is proposed. This allows an estimation of the surface equilibrium electric fields. They are 5.6 × 104, 1.1 × 105, and 5.7 × 105 V/cm for n = 1.9 × 1014, 7.1 × 1015, and 3.4 × 1017 cm−3, respectively. The surface of these samples has an inversion layer. In samples with n and p = 1016 − 1018 cm−3, the E0 and E0 + Δ0 peaks are displaced 0.02–0.03 eV to smaller energies relative to E0 of the purest sample, n = 1.9 × 1014 cm−3, which has E0 = Eg = 1.43 eV. This shift might be explained by tailing and impurity banding. In samples with n≳1018 cm−3, ER spectra are distorted and seem to be caused by the Moss-Burstein shift modulation. During ER measurements, galvanoluminescence (GL) appears for both n- and p-type samples. Measurements of GL vs voltage and time were made. GL spectra were measured for some n-type samples which agree with photoluminescence and cathodoluminescence. Maximum emitted power of radiation is ∼ 30 μW with quantum efficiency ∼ 10−4. A hole injection mechanism from the electrolyte qualitatively explains the behavior. During ER measurements by the electrolyte method, it is shown that it is necessary to take into account the appearance of GL since this effect can lead to erroneous ER results.
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