HIGH-EFFICIENCY INFRARED LIGHT-EMITTING-DIODES MADE IN LIQUID-PHASE EPITAXY AND MOLECULAR-BEAM EPITAXY HGCDTE LAYERS

We report in this article, for the first time the performance of light emitting diodes (LEDs) made in HgCdTe (MCT) epilayers on CdZnTe (CZT) lattice-matched substrates grown either by liquid phase epitaxy (LPE) or molecular beam epitaxy (MBE). Diodes are n/p homojunctions made by ion implantation. The MCT composition was chosen in order to get the emission wavelength between 3 and 5-mu-m. Electroluminescence spectra were recorded between 20 K and 300 K. A comparison of the two materials is made, demonstrating that they exhibit similar performances. Internal quantum efficiencies as high as 25% (lambda peak = 4.1-mu-m at 77 K) and 6% (lambda peak = 3.5-mu-m at 300 K) were obtained on both LPE and MBE materials and they reach a maximum for a temperature of about 90 K. For a material with lambda peak = 5.5-mu-m at 77 K, internal quantum efficiency remains as high as 5%. The external quantum efficiency is considerably increased using backside emission through the CZT substrate and optical coupling with a CZT lens: in such conditions 20% of the emitted light could be extracted from the structure. These results show that MCT can already be used for LEDs in the 3-5-mu-m region.