HgTe/HgCdTe superlattices grown on CdTe/Si by molecular beam epitaxy for infrared detection

High-quality HgTe/CdTe superlattices (SLs) and device structures incorporating them were grown by molecular beam epitaxy (MBE) on CdTe/Si substrates. In-situ techniques, such as reflection, high-energy electron diffraction and spectroscopic ellipsometry, were extensively used to rigorously control the growth parameters. The full width at half maximum (FWHM) of x-ray double-crystal rocking curves (DCRCs) were 100–150 arcsec, comparable to those of HgCdTe alloys grown on the same type of substrates. The room-temperature Fourier transform infrared (FTIR) spectrum exhibits two-dimensional features characteristic of SLs. Trial devices in a p⁺-n⁻-n⁺ format were fabricated by diffusing gold in order to further evaluate the HgTe/CdTe SL performance. Gold diffusion was chosen to fabricate photovoltaic junctions in order to preserve the structural integrity of the SLs during the device processing. Though no attempt was made in the current study to optimize the junction properties by Au diffusion, this method has proven to be very useful for rapid preliminary evaluation. The measured spectral-response and detectivity data indicate the possibility to fabricate photovoltaic devices on an HgTe/CdTe SL, although further work is needed to optimize the p-n junction fabrication.