InAs passivated gasb thermo-photovoltaic cells on a GaAs substrate grown by MOVPE

The high cost of Gallium Antimonide (GaSb) substrates offers a major obstacle to the commercial uptake of thermophotovoltaic technology. We present results on devices that could provide a route to the realisation of high efficiency and lower cost GaSb cells. Epitaxial GaSb has been grown by MOVPE (Metal-Organic Vapour Phase Epitaxy) on Gallium Arsenide (GaAs) and GaSb substrates and prototype thermo-photovoltaic devices have subsequently been fabricated. A number of growth series have been studied and leakage effects due to the lattice mismatch of 7.8% between GaAs and GaSb have been overcome. A low resistance Indium Arsenide (InAs) contact layer has been grown on the top surface of the cells and this is shown to increase the short circuit current of the cell. It is concluded that this is a passivation effect due to band bending caused by the Type III broken-gap heterojunction at the n-InAs/p-GaSb interface.