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Abstract: A significant difference in the growth mechanism of spatially closed structures of gallium nitride during selective growth in submicron windows with and without penetration into the GaN sublayer was demonstrated. The mechanisms of generation and development of dislocations, their role in the formation of self-organizing coaxial structures were modeled.

A combined experimental and modeling study of stress and curvature evolution during (0001) GaN growth on (0001) 4H‐SiC wafers is presented. It is shown that the GaN layers are under the compressive stress, whose magnitude depends on the composition of the AlGaN buffer that is used to accommodate the epitaxial strain between GaN and SiC. Processing of in situcurvature measurements suggests fast relaxation of the mismatch stress in GaN when the Al content is increased. At that, nucleation of new dislocations is possible, but the dislocation density decreases rapidly over a narrow part of the GaN layer due to large inclination and annihilation of the threading dislocations. Eventually, correlations between the curvature/stress/dislocation evolution and AlGaN buffer composition can be established and optimal strategy for the growth of crack‐free structures can be suggested.

InGaN‐based monolithic multi‐color light emitting diodes (LEDs) are studied both experimentally and theoretically with the focus on factors controlling their emission spectra and efficiency. A number of LEDs with different designs of spacers separating active regions providing blue and green light emission is examined. Unexpected behavior of the multi‐color LED efficiency is explained in terms of a simple balance model, assuming some degradation of materials quality of the green active region grown on top of the blue one. Electrical properties of spacers separating different active regions in the multi‐color LED structures are identified as the major factor controlling the contributions of these active regions to the total emission spectrum. Correlations between the type and level of the spacer doping and the emission spectrum are found by simulations. Alternative ways of the spectral control by using polarization doping in the graded‐composition InGaN and AlGaN alloys used as the spacers are suggested. Color characteristics of blue/green dual‐wavelength LEDs are also measured and discussed, regarding their possible applications. This paper considers various aspects of monolithic dual‐wavelength blue/green LEDs, from growth and characterization of LED structures to both experimental and theoretical analysis of their operation. Major factors controlling their emission spectra and efficiency are thoroughly studied and discussed.

Abstract

Optical phenomena in the mid-infrared range connected with interlevel and intersubband charge-carrier transitions in quantum dot and quantum well (QW) heterostructures under optical and electrical pumping were investigated. Spectra of interband photoluminescence are also presented. The existence of a metastable level in funnel-shaped QWs is experimentally confirmed. The intersubband transition dynamics in asymmetrical pairs of tunnel-coupled QWs was studied by means of pump-and-probe time-resolved spectroscopy. This paper was presented at the 3rd Russian Workshop on Nanophotonics, Nizhnii Novgorod, Russia, 26-29 March 2001.