MONOLITHIC INTEGRATION OF PBSE IR PHOTODIODES ON SI SUBSTRATES FOR NEAR-AMBIENT TEMPERATURE OPERATION

PhotovoltaiC IR detectors have been fabricated by a photolithographic process on lead selenide (PbSe) for near ambient temperature operation (200-300 K) in the 3-5 mum spectral band. The PbSe active layer has been grown by molecular beam epitaxy directly on a Si(111) substrate using a CaF2 buffer layer. The bulk, lateral and surface electrical effects which affect sensor performances have been investigated on variable-area diodes. The dark current is dominated by generation-recombination surface currents which are probably due to an inefficient surface passivation. The lateral collection of photocarriers increases the efficiency of the sensor at 300 K, the collection length is around 70 mum and the derived specific detectivity is around 3 x 10(9) cm Hz1/2 W-1.