MBE growth and device processing of MWIR HgCdTe on large area Si substrates

The traditional substrate of choice for HgCdTe material growth has been lat tice matched bulk CdZnTe material. However, as larger array sizes are requi red for future devices, it is evident that current size limitations of bulk substrates will become an issue and therefore large area Si substrates wil l become a requirement for HgCdTe growth in order to maintain the cost-effi ciency of future systems. As a result, traditional substrate mounting metho ds that use chemical compounds to adhere the substrate to the substrate hol der may pose significant technical challenges to the growth and fabrication of HgCdTe on large area Si substrates. For these reasons, non-contact (ind ium-free) substrate mounting was used to grow mid-wave infrared (MWIR) HgCd Te material on 3" CdTe/Si substrates. In order to maintain a constant epila yer temperature during HgCdTe nucleation, reflection high-energy electron d iffraction (RHEED) was implemented to develop a substrate temperature rampi ng profile for HgCdTe nucleation. The layers were characterized ex-situ usi ng Fourier transform infrared (FTIR) and etch pit density measurements to d etermine structural characteristics. Dislocation densities typically measur ed in the 9 x 10(6) cm(-2) to 1 x 10(7) cm(-2) range and showed a strong co rrelation between ramping profile and Cd composition, indicating the unique ness of the ramping profiles. Hall and photoconductive decay measurements w ere used to characterize the electrical properties of the layers. Additiona lly, both single element and 32 x 32 photovoltaic devices were fabricated f rom these layers. A RA value of 1.8 x 10(6) Omega -cm(2) measured at - 40 m V was obtained for MWIR material, which is comparable to HgCdTe grown on bu lk CdZnTe substrates.