MBE HGCDTE HETEROSTRUCTURE P-ON-N PLANAR INFRARED PHOTODIODES

We recently succeeded in fabricating planar Hg1-yCdyTe/Hg1-xCdxTe (x<y ) heterostructure photodiodes with the p-on-n configuration. Here we d iscuss early results in detail and present new results on an expanded range of infrared operation. The material used for this demonstration was grown by molecular beam epitaxy on lattice-matched CdZnTe substrat es. The p-on-n planar devices consist of an arsenic-doped p-type epila yer (y approximately 0.28) atop a long wavelength infrared n-type epil ayer (x = 0.22-0.23). The planar junctions were formed by selective po cket diffusion of arsenic deposited on the surface by ion implantation . Detailed analysis of the current-voltage characteristics of these di odes as a function of temperature shows that they have high performanc e and that their dark currents are diffusion-limited down to 52K. Low frequency noise measurements at a reverse bias voltage of 50 mV result ed in noise current values (at 1 Hz) as low as 1 X 10(-14) amps/Hz0.5 at 77K. Average RA values greater than 10(6) OMEGA-CM2 at 40K were obt ained for these devices with cut-off wavelength values in the 10.6 to 12 mum range. Seventy percent of these devices have R(o)A values great er than 10(5) OMEGA-cm2 at 40K; further studies are needed to improve device uniformity. These results represent the first demonstration tha t high performance long wavelength infrared devices operating at 40K c an be made using HgCdTe material grown by a vapor phase epitaxy growth technique.