HgCdTe buried multi-junction photodiodes fabricated by the liquid phase epitaxy

This article reports the parameters and characteristics of the new type of HgCdTe buried photodiodes operated at near-room temperature (T = 200-300 K) in long wavelength infrared spectral range. The liquid phase epitaxy (LPE) Hg1-xCdxTe (x = 0.16-0.20) layers were grown on holes etched in (10 0) CdZnTe substrate. Prior to layer deposition, the CdZnTe substrate has been etched to form the bars on 30 mum centers and 20 mum depth. Next, 20-mum thick HgCdTe epitaxial layer has been grown from Te-rich solution. The type of conductivity was controlled by deliberately doping with indium (n-type) and Sb (p-type). The Nomarski microscopy showed that the surface of specially prepared layers was flat and the composition of layers, measured by Fourier transform infrared microscopy, was homogenous. Samples were cleaved and examined in cross section by scanning electron microscopy. Finally, serial connected multi-junction photodiodes have been fabricated. It is shown that LPE can be used to realise advanced bandgap engineered multi-junction structures. This conclusion is supported by device quality characteristics: spectral response and detectivity. (C) 2002 Published by Elsevier Science B.V.