Electrical conduction through compound semiconductor wafer bonded interfaces

Abstract

The recent introduction of a family of very high-efficiency transparent-substrate (TS) ( Al x Ga 1 −x) 0.5 In 0.5 P GaP LEDs was made possible by the development of advanced compound semiconductor wafer bonding techniques, including techniques for producing wafer bonded interfaces that exhibit low-resistance ohmic electrical conduction. These LEDs are fabricated by selectively removing the GaAs substrate from an absorbing substrate (AS) ( Al x Ga 1 − x) 0.5 In 0.5 P GaAs LED wafer and replacing it with a transparent GaP wafer. The resulting TS LED lamps are twice as efficient as the original AS LED lamps (luminous flux and power efficiency) due to the improved light extraction resulting from the transparent GaP substrate, and to the low electrical resistance of the wafer-bonded interface. Techniques for fabricating these low-resistance compound semiconductor wafer-bonded interfaces will be discussed, as well as results of electrical evaluations and microscopic examinations of the wafer-bonded interfaces.