width at half-maximum (FWHM) of less than 10 meV for PL peak emission < 1.9 prn. PL FWHM increased to 30 meV for peak emission -2.12 pm for OMVPE-grown layers. Nominally undoped layers are p-type with typical 300 K hole concentration of -9 x 1015 cm-3 and hole mobility -450 to 580 cm*N-s €or OMVPE-grown layers. p-and n-type doping is reported for layers grown with either technique. The ideaiity factor of diode structures is -2 for both techniques. INTRODUCTIONThermophotovoltaic systems in which thermal radiation is converted to electricity through the use of a photovokaic cell, are experiencing revived interest as the properties of low-bandgap semiconductor materials continue to improve [I]. To achieve high utilization of thermal radiation. the semiconductor cutof€ wavelength should closely match the dominant wavelength of rhe thermal source. For TPV system operating in the temperature range 1 100 to 1 SOW, the peak in emissive power varies from 1.9 to 2.6 pm. This wavelength range can be satisfied b y Gol-,In,As~-~Sb, 2 , alloys which can be grown lattice-matched to either InAs or GaSb rubstrares. However, this alloy system exhibits a large miscibility gap [2,3] which limits the equilibrium p w t h of srable alloys to a cutoff wavelength of 2.39 pm [4]. By using nonequilibrium growth techniques such as mofecular beam epitaxy (MBE) and organometallic