혼합소스 HVPE법에 의한 질화물 반도체 발광다이오드

Abstract

Ⅲ-Nitride semiconductor light emitting diodes (LEDs) were fabricated by mixed-source HVPE. The LED structure was made of p-n junction with double heterostructure. For the growth of the LED structure, multisliding boat system was introduced to the mixed-source HVPE. And mask was designed for selective area growth of the LED structure.

The double heterostructure of the LED was composed of Te-doped AlGaN as n-cladding layer, InGaN as active layer, Mg-doped AlGaN as p-cladding layer, and Mg-doped GaN as p-capping layer. Prior to growth of the double heterostructure, single layers which consist of the LED structure were grown by the mixed-source HVPE, respectively. Thecrystal quality, composition, and concentration of the layers were characterized by XRD, XPS, and Hall measurements.

The Al composition of the AlGaN layers was controlled by variation of temperature of source zone. In case of the LED structure, the composition of Al was in control of 16%. The carrier concentrations of Te-doped AlGaN layer were controlled by change of Te atomic fractions in the mixed-source. For the LED structure, the carrier concentration of the Te-doped AlGaN cladding layer was controlled in the order of 1ⅹ1018 cm-3. The hole concentrations of Mg-doped AlGaN layer and Mg-GaN layer were controlled by Mg atomic fraction in the mixed-source.

The hole concentration of the Mg-doped GaN was controlled in the order of 3ⅹ1017 cm-3. In the InGaN active layer, the composition of In was in control of 10%.

The double heterostructure was grown consecutively by the mixedsource HVPE using the multi-sliding boat system. The side facets were consisted of pyramidal and inverse pyramidal shape for efficient light extraction. The characteristics of the LED were evaluated by I-V and electroluminescence. Even though the LED grown by the mixed-source HVPE need to be more improved in optical and electrical properties, it is worth to note that newly developed method of Ⅲ-Nitride semiconductor LED could be a candidate technology for the fabrication of low cost LEDs.