Stacking fault-associated polarised surface-emitted photoluminescence from zincblende InGaN/GaN quantum wells

A photoluminescence (PL) study was performed on zincblende-InGaN/GaN quantum wells. These structures contained a high density of stacking faults, which cause the segregation of indium at the intersection with the quantum wells, creating quantum wires. Emission from these quantum wires dominates the room temperature PL spectra and is highly polarised (Fig 1): emission from the quantum wells is additionally observed at 10K (Fig 2). The 10K PL decays show that the emission from the quantum wells is fast and mono-exponential, and the quantum wire emission is a stretched exponential (Fig 3). 10K PL-excitation measurements show absorption into the GaN barriers, which does not shift with emission energy. Absorption into the quantum well is observed and does not shift with emission energy over the quantum wire emission (Fig 5). Low temperature PL spectra show emission from the quantum wells and wires (Fig S1). As the temperature is increased, the quantum well emission quenches at a faster rate than the wire emission and the peaks redshift (Fig. S2). As the excitation power is increased, there is no change in the PL spectra (Fig S3). Changing the polarisation of the excitation has no effect on the PL or PL-excitation spectra (Fig S4). Simple calculations were performed to calculate the band profile and carrier ground states in quantum wire structures (Fig S5). An estimation of the ground and excitated hole state energies was also calculated (Fig S6). This allowed a calculation of the change in the degree of linear polarisation of the quantum wire emission at 300K, compared with 10K (Fig S7).

本研究针对闪锌矿结构InGaN/GaN量子阱开展了光致发光（photoluminescence, PL）研究。该类结构具有高密度堆垛层错，堆垛层错会在与量子阱的交界面处引发铟元素偏析，进而形成量子线。该量子线的发光主导了室温下的PL光谱，且具有高度的偏振特性（图1）；而在10K低温下还可观测到量子阱的发光信号（图2）。10K下的PL衰变动力学测试表明，量子阱的发光衰减为快速单指数过程，而量子线的发光衰减则为拉伸指数过程（图3）。10K下的PL激发测试显示，GaN势垒存在吸收峰，且该吸收峰不随发光能量发生偏移；同时还观测到量子阱的吸收峰，其在量子线发光能量范围内同样不随发光能量偏移（图5）。低温PL光谱可观测到量子阱与量子线的发光信号（补充图S1）。随着温度升高，量子阱发光的猝灭速率快于量子线发光，且两个发光峰均发生红移（补充图S2）。提升激发功率时，PL光谱无明显变化（补充图S3）。改变激发光的偏振特性，不会对PL光谱或PL激发光谱产生影响（补充图S4）。本研究开展了简单的数值计算，以求解量子线结构的能带分布与载流子基态能级（补充图S5）。同时还估算了基态与激发态空穴的能级（补充图S6）。基于上述计算结果，本研究进一步计算了300K与10K下量子线发光的线偏振度变化（补充图S7）。