Photoelectrical properties of n-GaAs-p-A[subx]-[subx]As heterojunctions.

Measurements on the wavelength and temperature dependences of the short-circuit current and open-circuit voltage of n-GaAs-p-AlGaAs (Ge-doped) heterojunctions under parallel illumination are reported. The results are explained using the theory of photoelectrical effects in ideal heterojunctions. Distinct contributions from each side of the heterojunctions were evidenced in the photoresponse spectra. The influence of heterojunction parameters on the photoelectrical response is discussed.
One of the fields in which the use of heterojunctions seems to be most promising is that of light conversion, in such devices as photodetectors or solar cells. The study of photoelectrical effects in heterojunctions is thus of increasing importance, from both applicative and fundamental points of view, as it also yields precious information concerning the properties of the materials which form the heterojunction.
Unfortunately, the performances of heterojunction devices are seriously limited by the existence of interface states, acting as traps or recombination centres. However, the pair GaAs-Al<SUBx>Ga<SUB1-x>As represents a fortunate exception, the two semiconductors having very close lattice constants, which made possible the preparation of almost ideal heterojunctions, i.e. with a small density of interface states, so that their effect is negligible (Alferov et al. 1968).
A first paper reporting some photoelectrical measurements on GaAs-Al<SUBx>Ga<SUB1-x>As heterojunctions is due to the group of J. I. Alferov (1969), who also published works on solar cells (Alferov et al. 1970) and selective heterophotoelements (Alferov et al. 1971) based on this heterojunction pair.
Recently Woodall and Hovel (1972) reported the realization of GaAs-Al<SUBx>Ga<SUB1-x>As solar cells with higher conversion efficiencies than the best silicon homojunction cells.
The purpose of the present paper is to make a more detailed study of the photoelectrical properties of... [ABSTRACT FROM AUTHOR]