Semiconductor III-nitride heterostructures are important for light emission in the ultraviolet and visible ranges [1]. Typical III-nitride based light emitting structures with InGaN/GaN quantum wells QWs are grown along the strongly polarized 0001 direction [2]. The associated quantum-confined Stark effect QCSE reduces the overlap between the electron and hole wave functions and results in the reduction of the internal quantum efficiency IQE [3]. The QCSE strongly depends on the crystallographic orientation. In nonpolar and semipolar QWs, QCSE can be completely or partially eliminated which can potentially enhance the performance of light emitting devices. Experimental observation for the absence of QCSE in nonpolar AlGaN/GaN (10-10) and (11-20) QWs has been reported [4, 5] A reduced QCSE has also been observed in (11-22) and (101-3) semipolar InGaN/GaN QWs [6, 7]. However, planar nonpolar and semipolar III-nitride films grown on r- and m-plane sapphire by MOVPE (Metalorganic vapour phase epitaxy).
semiconductor, heterostructure, orientation, sapphire, emission energy
In order to demonstrate good quality of the overgrown semi-polar GaN films on nano-rod templates, an InGaN/GaN MQW structure has been grown after the overgrowth to investigate optical performance of the semi-polar MQWs. Figure 1 is a schematic figure. The InGaN/GaN MQW structure is composed of 10 period InGaN well and GaN barrier thickness with 2.5 nm and 8.5 nm, respectively. Meanwhile, identical InGaN/GaN MQW structures are grown under the c-plane InGaN/GaN MQW growth conditions on an as-grown semi-polar GaN and a standard c-plane GaN template in order to make comparisons. Note that the growth conditions for InGaN/GaN QWs are not optimized.
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