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The influence of (NH4)2S treatment on the surface properties of GaP is presented for the first time. Changes in the chemical composition and Fermi level position are characterized using X-ray photoelectron spectroscopy. These measurements show that after surface treatment, the GaP surface is free of native oxides. A strong enhancement (~ 50 times) in the cathodoluminescent efficiency was observed for sulfur passivated samples. Schottky diode characteristics were used to reveal changes in the barrier height and interface state density due to surface treatment. Changes in carrier concentration were also found to be reflected in measured Raman spectra. The passivation mechanism is also briefly discussed.

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We report on radioluminescence (RL) studies of the wide band gap semiconductors GaP and GaInAsP exposed to tritium gas. All samples were prepared by liquid phase epitaxy. RL tests were performed as a function of tritium pressure, sample temperature, and time, enabling the limiting factors for developing high efficiency visible RL sources to be identified. The studies were complemented by photoluminescence (PL) and cathodoluminescence (CL) measurements. Reduction of surface recombination velocity was shown to be essential for obtaining low threshold CL response and improved PL efficiency. This factor resulted in tritium-activated RL visible to the naked eye. With appropriate materials optimization, these structures should be suitable for developing high efficiency RL devices.