Linear Electro-Optic Photoreflectance Spectra of GaAs and CdTe around E1 and E1 + Δ1

Abstract

We report on the measurement of linear electro‐optic (LEO) photoreflectance (PR) spectra for both GaAs and CdTe (001) crystals. It is found that the amplitude of the LEO spectra is directly related to the sample doping level, while the sign of these spectra is dependent on the conductivity type of the sample. GaAs LEO spectral lineshapes, in contrast, are found to be independent of the conductivity type in the 1015 to 1017 cm—3 impurity range. These facts, along with a precise theoretical understanding of the LEO spectra, allow for the use of LEO‐PR spectroscopy for the characterization of surface and interface electric fields.

In situ reflectance-difference spectroscopy of doped CdTe and ZnTe grown by molecular beam epitaxy

“…The theoretical model gives an analytical expression for the normalized change in reflectivity and was successfully tested ex situ for GaAs and CdTe, where the LEO component was isolated by means of photoreflectance measurements ͑PR͒. 13,14 It is noted, however, that besides the LEO contribution to the RD spectra, additional components associated to different physical origins could be present, such as surface reconstruction [15][16][17][18] and linear defects. 9 Therefore, to obtain a LEO line shape it is necessary to substract from the overall RD spectrum the non-LEO contribution.…”

Measurement of the Surface Strain Induced by Reconstructed Surfaces of GaAs (001) Using Photoreflectance and Reflectance-Difference Spectroscopies

“…Nondestructive probes, such as optical ones, are therefore of prime importance to study the complex phenomena associated with such surfaces. Reflectance-difference spectroscopy (RDS) and photoreflectance difference (PR-D) spectroscopy are two complementary techniques that have been used for the characterization of GaAs (001) surfaces [1][2][3][4][5][6][7].…”

“…PR-D is a very sensitive tool for the characterization of the surface electric field associated to band bending (for values down to 10 3 V=cm) [2] and for the study of the piezo-optical properties of semiconductors [3]. For crystals of zincblende symmetry (T d ) PR-D spectra involve only a linear electro-optic (LEO) component as, for this symmetry, the quadratic electro-optic (QEO) PR component is isotropic [1].…”

“…A similar discussion applies to the E 1 1 transitions. (2) The left side of Fig. 2 shows the evolution of the PR-D spectrum as the surface reconstruction changes from c4 4 to 2 4.…”

Influence of anisotropic in-plane strain on critical point resonances in reflectance difference data

“…1 In materials with an isotropic bulk, optical anisotropies are therefore associated mainly with the surface optical response. In this regard, it has been shown that RD spectroscopy is very sensitive to surface electric fields in zinc blende semiconductors due to Fermi level pinning by surface states, 12,13 and anisotropic strain fields due to the presence of 60°dislocations. This optical technique, however, yields information not only on surface phenomena, but in general on any semiconductor domain where the cubic symmetry has been altered by any perturbation.…”