An InGaN/InGaN multiquantum well (MQW) structure with a reduced internal electric field is grown, and compared with a conventional InGaN/GaN MQW structure. Time-integrated and time-resolved photoluminescence (PL) are measured as a function of an external bias voltage. The flatband condition, in which the external bias voltage completely compensates the internal electric field, is found by a measurement of PL peak energy as a function of bias voltage. From the measurement of the integrated PL intensity and the PL lifetime, we observe that tunneling has an important role in the carrier decay process of the biased MQW structure. Using the flatband condition, the internal electric field is calculated to be 1.75 and 2.15 MV/cm for InGaN/InGaN and InGaN/GaN structures, respectively.
Nonpolar a-plane (11-20) GaN (a-GaN) layers with low overall defect density and high crystalline quality were grown on r-plane sapphire substrates using etched a-GaN. The a-GaN layer was etched by pulse NH3 interrupted etching. Subsequently, a 2-µm-thick Si-doped a-GaN layer was regrown on the etched a-GaN layer. A fully coalescent n-type a-GaN layer with a low threading dislocation density (~7.5 × 10(8) cm(-2)) and a low basal stacking fault density (~1.8 × 10(5) cm(-1)) was obtained. Compared with a planar sample, the full width at half maximum of the (11-20) X-ray rocking curve was significantly decreased to 518 arcsec along the c-axis direction and 562 arcsec along the m-axis direction.
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