Yoshita M, Liu S M, Okano M, Hayamizu Y, Akiyama H, Pfeiffer L N, West K W
Institute for Solid State Physics (ISSP), University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8581, Japan. CREST, JST, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8581, Japan.
J Phys Condens Matter. 2007 Jul 25;19(29):295217. doi: 10.1088/0953-8984/19/29/295217. Epub 2007 Jun 11.
T-shaped GaAs quantum-wire (T-wire) lasers fabricated by the cleaved-edge overgrowth method with molecular beam epitaxy on the interface improved by a growth-interrupt high-temperature anneal are measured to study the laser device physics and fundamental many-body physics in clean one-dimensional (1D) systems. A current-injection T-wire laser that has 20 periods of T-wires in the active region and a 0.5 mm long cavity with high-reflection coatings shows a low threshold current of 0.27 mA at 30 K. The origin of the laser gain above the lasing threshold is studied with the high-quality T-wire lasers by means of optical pumping. The lasing energy is about 5 meV below the photoluminescence (PL) peak of free excitons, and is on the electron-hole (e-h) plasma PL band at a high e-h carrier density. The observed energy shift excludes the laser gain due to free excitons, and it suggests a contribution from the e-h plasma instead. A systematic micro-PL study reveals that the PL evolves with the e-h density from a sharp exciton peak, via a biexciton peak, to an e-h-plasma PL band. The data demonstrate an important role of biexcitons in the exciton Mott transition. Comparison with microscopic theories points out some problems in the picture of the exciton Mott transition.
通过分子束外延的解理边缘过生长方法制备的T形砷化镓量子线（T线）激光器，其界面通过生长中断高温退火得到改善，对其进行测量以研究清洁一维（1D）系统中的激光器件物理和基本多体物理。一种在有源区具有20个周期T线且腔长为0.5毫米并带有高反射涂层的电流注入T线激光器，在30K时显示出0.27毫安的低阈值电流。利用高质量的T线激光器通过光泵浦研究激光阈值以上激光增益的起源。激光能量比自由激子的光致发光（PL）峰值低约5毫电子伏，并且在高电子 - 空穴（e - h）载流子密度下处于电子 - 空穴（e - h）等离子体PL带上。观察到的能量偏移排除了自由激子导致的激光增益，这表明是e - h等离子体的贡献。系统的微PL研究表明，PL随着e - h密度从尖锐的激子峰，经过双激子峰，演变为e - h等离子体PL带。数据证明了双激子在激子莫特转变中的重要作用。与微观理论的比较指出了激子莫特转变图景中的一些问题。
