GaAlAsSb quaternary alloys and GaAlSb ternary alloys have been grown by liquid phase epitaxy (LPE) at 550°C and 450°C, respectively. The material compositions and epitaxial structures are suitable for fabricating photodiodes sensitive in the1.0-1.8 mum wavelength range. Various avalanche photodiode structures fabricated in these materials are discussed. The ion implanted GaAlAsSb APD's exhibit a high gain of 100, 82 percent quantum efficiency, and a FWHM of 400 ps. The heterojunction GaAlAsSb APD's have a gain of 40, 92 percent quantum efficiency, and a FWTM of 150 ps. The only remaining material problem which limits the performance of these devices is the high-surface leakage current.