Electroluminescence and Electrical Properties of High-Purity Vapor-Grown GaP

The electroluminescence, Hall coefficient, and resistivity of high-purity GaP, grown by means of vaporphase epitaxy on bulk single-crystal GaP substrates, have been studied as functions of temperature. Hall mobilities as high as 2730 and 189 cm2/V sec have been obtained at 77° and 300°K, respectively. The electroluminescence (EL) of diodes fabricated by Zn diffusion exhibits intrinsic recombination. At 77°K, in addition to the narrow no-phonon line due to bound exciton recombination at a neutral donor site, the near-band-edge EL exhibits a well-defined series of peaks corresponding to the phonon-assisted recombination of free excitons. Peaks are observed associated with both the absorption and emission of TA, LA, and TO phonons with energies of 12.5, 31.0, and 44.0 meV, respectively. The intensities of the peaks associated with phonon emission have the approximate ratio 1:3:1.5 for the TO, LA, and TA phonons, respectively. These energies and relative intensities are in good agreement with absorption and cathodoluminescence data for intrinsic GaP. The temperature dependence of the electroluminescence demonstrates that in these devices, which have a low concentration of nitrogen and other unintentional impurities, the 300°K emission is dominated by intrinsic recombination.