Cylindrical microcavity light emitters realized with double-oxide-confinement or single-defect photonic bandgap crystals

The confinement of light in one, two, and three dimensions on a wavelength-scale can lead to light emitting devices with enhanced efficiency, narrow spectral linewidth, improved directionality, and even enhanced spontaneous recombination rate (Yokoyama, 1992). In this paper, we describe the design, fabrication and characteristics of electroluminescent cylindrical microcavity surface emitters realized either by double oxide confinement or as a photonic bandgap (PBG) microcavity. In the latter, a single "point defect" in a 2D photonic crystal traps light and serves as a true microcavity. Comparison of different lateral confinement structures is made. Double oxide-confined devices are made with InP-based heterostructures (/spl lambda/=1.55 /spl mu/m) and consist of either InGaAs (bulk) or InGaAsP-InP pseudomorphic MQW recombination regions buried in InGaAsP or InP spacers of thickness /spl lambda//n. 120 nm thick In/sub 0.52/Al/sub 0.48/As layers are incorporated on both top and bottom of the cavity and appropriate p-type (top) and n-type (bottom) contact layers are included on both sides. The lateral microcavity size, defined by oxide confinement, ranges from 1 /spl mu/m to 30 /spl mu/m. PBG-based devices are made with GaAs-based heterostructures, which consist of an InGaAs MQW /spl lambda/-cavity (/spl lambda/=0.94 /spl mu/m). The 2D PBG formation is achieved by e-beam lithography and deep dry etching techniques. Single or multiple defects in the center define the /spl lambda/-sized microcavity. The PBG was designed to be centered around the cavity peak emission wavelength at 0.94 /spl mu/m.