EFFICIENCY ENHANCEMENT OF INDIRECT GAP LIGHT-EMITTING DEVICES
Original Publication Date: 1978-Dec-31
Included in the Prior Art Database: 2004-Mar-31
Xerox Disclosure Journal
Light-emitting devices are commonly fabricated using semicon-ductor materials having both direct and indirect forbidden energy gaps- In the latter, the lowest empty conduction states do not have the same crystal momentum as the highest filled valence states, For such indirect band gap semicon-ductors, the emission wavelength is determined by the amount of defects (normally chemical impurities) in the host semicon-ductor, There is continuing effort to increase the efficiency of these devices, A scheme is proposed here whereby the efficiency for any light-emitting device fabricated from an indirect gap semiconductor host can have its efficiency enhanced, The enhancement is obtained by applying an external electromagnetic field in the region (normally field-free) where electron-hole recombination occurs, The efficiency increase depends on the field strength along a critical crystallographic direction characterized by the host material and dopant.