Using reach-through techniques to improve the external power efficiency of silicon CMOS light emitting devices

For CMOS silicon-based light emitting devices to become practical the external power efficiency must be increased. In this paper a reach-through technique is described whereby the external power efficiency can be increased as a result of three phenomena: i) increase in internal quantum efficiency, ii) increase in light extraction efficiency, and iii) lower operating voltage. The three techniques are discussed and the factor 7 improvement in external power efficiency will be described in terms of the electrical characteristics as well as the external radiation patterns.