In this paper, we report on the low pressure organometallic chemical vapor deposition of AlInAs lattice matched to InP and the effect of the substrate temperature and V/III ratio on the layers grown. High quality AlInAs with X-ray and photoluminescence (5 K) linewidths of 21 arc sec and 15 meV, respectively, was obtained. It is demonstrated that a high growth temperature and a high arisine flow rate are necessary for obtaining good electrical and optical properties. A discrepancy was shown to exist between C- V and Hall derived carrier concentrations probably due to deep levels affecting the C - V measurements and a two-dimensional electron gas (2DEG) at the AlInAs/InP interface affecting the Hall measurements. The existence of a 2DEG at the AlInAs/InP interface, with a sheet density of 2.9 x 10(11) cm-2 and a mobility of 11050 cm2/V.s at 4 K, was shown using Shubnikov-De Haas measurements. A correlation was made between oxygen or an oxygen related complex and high C - V measured carrier concentrations and large leakage currents in reverse biased Schottky contacts. An intense emission at approximately 1.2 eV, present in 5 K photoluminescence spectra of AlInAs/InP, was attributed to a spatially indirect transition across the AlInAs/InP interface. Conduction and valence band offsets of 448.8 and 324.3 meV, respectively, were deduced from the energy of this transition. Self aligned 0.25-mu-m gate high electron mobility AlInAs/GaInAs transistors with a transconductance as high as 1150 mS/mm and f(t) = 80 GHz at room temperature were fabricated. Finally, metal-semiconductor-metal photodetectors with a leakage current as low as 5 nA at 5 V, breakdown voltage greater than 25 V, responsivity of 0.42 A/W at 1.3-mu-m wavelength, and a bandwidth of 8 GHz were demonstrated.