A NEW APPROACH TO WIDE-BAND GAP VISIBLE-LIGHT EMITTERS

We report on a new approach to the fabrication of visible-light emitte rs from wide bandgap semiconductors. Our structures avoid the ohmic co ntacting problems which have been encountered in p-ZnSe:N devices by u sing only the doping types which tend to occur naturally in II-VI semi conductors. Specifically, we choose the closely lattice-matched n-CdSe /p-ZnTe heterojunction. To overcome the type-II blocking band alignmen t of this heterojunction, we introduce a graded alloy region which all ows injection of electrons into the ZnTe while retaining the blocking offset in the valence band to inhibit injection of holes into the CdSe . Room temperature electrical characteristics and electroluminescence spectra confirm the effectiveness of this approach. Finally, we show h ow the emission wavelength can be shifted to blue wavelengths and beyo nd by expanding the bandgap of the recombination region with a MgyZn1- y Te alloy.