Thin Solid Films 451 – 452 (2004) 124–127 0040-6090/04/$ - see front matter  2003 Elsevier B.V. All rights reserved. doi:10.1016/j.tsf.2003.10.117 Liquid-phase electroepitaxial growth of low band-gap p-InAsPSb y n-InAs and p-InAsP y n-InAs diode heterostructures for thermo-photovoltaic application V.A. Gevorkyan *, V.M. Aroutiounian , K.M. Gambaryan , M.S. Kazaryan , K.J. Touryan , a, a a a b M.W. Wanlass b Department of Radiophysics, Yerevan State University, 1 A.Manoukian Str., Yerevan 375049, Armenia a National Renewable Energy Laboratory (NREL), Golden, CO, USA b Abstract This report describes our efforts to fabricate InAsPyInAs and InAsPSbyInAs epitaxial diode heterostructures for TPV converter applications. For the growth of these TPV-structures the new version of liquid-phase electroepitaxy has been employed. First type of structure consists of the n-InAs (111)B substrate and compositionally graded p-InAsP layer with the increasing concentration of phosphorus from impurity levels up to 6%, along the growth direction. The second type of structure consists of p-InAsPSb layer directly grown on a n-InAs (100) substrate. These structures have a uniform thickness, a mirror-like surface and a very flat interface. The dislocation density on the surface layer was no more than N s10 cm . The I –V and C–V characteristics of n- 5 y2 D InAsyp-InAsP and n-InAsyp-InAsPSb TPV structures have been investigated. The spectral response of these diode structures has been measured. The results of these studies show that the second type of TPV structures has better performance than the first type.  2003 Elsevier B.V. All rights reserved. PACS: 73.40 K; 72.40 Keywords: Liquid phase electroepitaxy; Thermophotovoltaic converters; IR-photodetectors 1. Introduction Renewable energy technologies present an economi- cally viable alternative to traditional energy sources today. Beside traditional solar cells, photovoltaic (PV) elements have found wide use in thermophotovoltaic (TPV) power converters recently w1x. TPV power gen- eration involves the conversion of solar or other thermal energy to electrical energy through the use of PV converters that respond to middle-wavelength infrared radiation. Recently, there has been a strong interest in TPV technology w2,3x, in part, due to the development of high efficient low band-gap semiconductor PV converters. TPV energy conversion systems consist of a radiant heat source, a selective optical filter and a TPV cell, *Corresponding author. Tel.yfax: q3741-555590. E-mail address: vgev@ysu.am (V.A. Gevorkyan). which is a semiconductor p-n junction. Input power to the TPV cell is provided by a heat source, which has a high emitter temperature. The emitter temperature (1000–2000 8C) is generally dictated by practical con- straints: low temperature results in low TPV converter electrical power output and long system lifetime, while the opposite is true at high temperatures. TPVs are low direct-band gap semiconductors that can convert all photons with energies higher or equal to their band gap, which is typically close to the energy corresponding to the irradiant peak in the emitter spec- trum. The main difference between solar cells and TPV systems is that a selective optical filter is used to reflect the radiation that cannot be absorbed by the TPV cell, back to the emitter to re-heat it. This improves the TPV system efficiency and keeps the converter and its support structure cooler. Unlike solar cells, the power density is significantly larger in TPV systems since the source is very close to the cell.