UNIFORM LOW DEFECT DENSITY MOLECULAR-BEAM EPITAXIAL HGCDTE

This paper describes recent advances in MBE HgCdTe technology. A new 3 inch production molecular beam epitaxy (MBE) system, Riber Model 32P, was installed at Rockwell in 1994. The growth technology developed ov er the years at Rockwell using the Riber 2300 R&D system was transferr ed to the 32P system in less than six months. This short period of tec hnology transfer attests to our understanding of the MBE HgCdTe growth dynamics and the key growth parameters. Device quality material is be ing grown routinely in this new system. Further advances have been mad e to achieve better growth control. One of the biggest challenges in t he growth of MBE HgCdTe is the day-to-day control of the substrate sur face temperature at nucleation and during growth. This paper describes techniques that have led to growth temperature reproducibility within +/-1 degrees C, and a variation in temperature during substrate rotat ion within 0.5 degrees C. The rotation of the substrate during growth has improved the uniformity of the grown layers. The measured uniformi ty data on composition for a typical 3 cm x 3 cm MBE HgCdTe/CdZnTe sho ws the average and standard deviation values of 0.229 and 0.0006, resp ectively. Similarly, the average and standard deviation for the layer thickness are 7.5 and 0.06 mu m, respectively. P-on-n LWIR test struct ure photodiodes fabricated using material grown by the new system and using rotation during growth have resulted in high-performance (R(0)A, quantum efficiency) devices at 77 and 40K. In addition, 128 x 28 foca l plane arrays with excellent performance and operability have been de monstrated.