A. Zegadi

Photoacoustic spectroscopy of defect states in CuInSe2 single crystals

Abstract Photoacoustic spectra have been obtained at room temperature from n and p-type single crystals of CuInSe 2 grown from a near-stoichiometric melt by the vertical Bridgman technique. The spectra have been used to evaluate gap energies and also to establish ionisation energies for several deep defect-related energy states. The data reported here demonstrate that the photoacoustic technique is useful as a contact-less method of appraising the complex intrinsic defect populations which dominate the optoelectronic properties of this semiconducting compound.

A photoacoustic spectrometer for measuring subgap absorption spectra of semiconductors

In this paper we describe the design of a high resolution near‐infrared photoacoustic spectrometer of the gas‐microphone type intended to be used for measuring impurity absorption spectra of semiconductors. Particular attention has been paid to the design of the photoacoustic cell to find the most suitable one, and as a result, several cells differing in geometry and materials have been investigated. We present results for the PA amplitude dependence on the modulating frequency for carbon black powder and some widely used semiconductors. The sensitivity of the spectrometer and its effectiveness in resolving active defect states existing in the subgap absorption spectra of semiconductors are demonstrated in both optically opaque and transparent thick and thin samples.

Photoacoustic spectroscopy of CuInSe2 thin films

Abstract Polycrystalline CuInSe 2 thin films grown by the three-source co-evaporation technique are assessed near their fundamental absorption edge with a high resolution photoacoustic spectrometer of the gas-microphone type. The results are presented for films differing in uniformity, composition and thickness. The effect of heat treatment in various ambients on the properties of these films have also been investigated using in addition to photoacoustic spectroscopy, X-ray diffraction, Rutherford backscattering spectroscopy and scanning electron microscopy.

Optical properties of flash-evaporated CuIn0.75Ga0.25Se2 thin films by photoacoustic spectroscopy

Abstract A high-resolution near-infrared photoacoustic spectrometer of the gas-microphone type is used for room-temperature analysis (in the subgap region of the spectrum) of non-radiative defect levels in as-grown CuIn0.75Ga0.25Se2 thin films. Films were grown by flash evaporation onto glass substrates at 200 °C. The absorption coefficient has been derived from the photoacoustic spectra to determine the gap energy and establish the activation energies for several defect-related energy levels. We also present preliminary results relating to the influence of post-deposition heat treatments in a selenium atmosphere on the photoacoustic spectral response. The improvements in the photoacoustic spectrum following annealing are directly correlated with the sample compositional, structural and electrical properties. Finally, the effect of interference on the photoacoustic spectra is discussed.

Photoacoustic spectroscopy use in the analysis of ion‐implanted CuInSe2 single crystals

A high‐resolution near‐infrared photoacoustic spectrometer of the gas–microphone type is used for room‐temperature analysis of the defect states in ion‐implanted CuInSe2 single crystals. A wide range of ions differing in their masses as well as in their electrical activities in the host crystal (O+, Ne+, Cu+, Xe+, and Li+) have been implanted at various energies and doses to assess the technique sensitivity to detect changes affecting the compound subgap absorption spectrum, which is characteristic of impurities. The detected changes (either by the appearance of new peaks or by a change in the impurity or defect concentrations) are shown to differ from one ion species to another. The depth profiling capability of the technique in analyzing implanted samples is also discussed. The results obtained here are correlated to existing published data. It is shown that photoacoustic spectrometry can be very useful if used to appraise the complex defect structure of ion‐implanted CuInSe2.

An electron microscope study of near-surface damage caused by Xe and Ne ion implantation in CuInSe2 single crystals

Abstract In this paper, we present the first SEM comparative study of the damage induced on the near-surface of CuInSe 2 single crystals following implantation with ions of neon and xenon. We show that whilst neon ions have hardly affected the appearance of the CuInSe 2 surface, xenon ions have led to preferential sputtering and to the formation of gas bubbles trapped near to the surface. After reaching their saturation levels these bubbles have led to gas release. The experimental results are correlated with TRIM calculations.

The effect of Se content on defect levels in CuInSe/sub 2/ single crystals detected by photoacoustic spectrometry

The objective of this paper is to investigate the impact of changes in the selenium content of thin-film solar cell CuInSe/sub 2/ single crystals on their optical properties in the subgap region of the infrared spectrum. A high resolution near-infrared photoacoustic spectrometer of the gas-microphone type is used for room temperature analysis of nonradiative defect states in as-grown n and p-type CIS crystals. Samples with an excess and a deficiency of Se (5% off the stoichiometric composition), were grown from the melt by the vertical Bridgman technique. The absorption coefficient has been derived from photoacoustic spectra in order to establish activation energies for several defect-related energy levels.