Electricity generation from thermal irradiation governed by GaSb diode has been systematically investigated in its normal and inverted configuration. It is demonstrated here that there is a critical base doping, 3 x 10(17) cm(-3), for the normal structure, and the superior output performance of p(+)/n structure with low base-doping would completely be switched to the n(+)/p structure when base doping larger than this critical one. Moreover, a spectrum-independent optimal doping concentration, N-a = 1.5 x 10(17) cm(-3), is also observed for n(+)/p structure, and no doping-dependent thickness compensation between emitter and base layer can be observed for the inverted structure. To save the material consumption and device cost, the reasonable active layer can be constructed by 100-200 nm emitter and 5-7 mu m base, offering the useful guideline to fabricate the GaSb cell on the economical but lattice-mismatched heterosubstrate. (C) 2012 Elsevier Ltd. All rights reserved.