Kappei L, Szczytko J, Morier-Genoud F, Deveaud B
Ecole Polytechnique Fédérale de Lausanne, EPFL, CH-1015 Lausanne, Switzerland.
Phys Rev Lett. 2005 Apr 15;94(14):147403. doi: 10.1103/PhysRevLett.94.147403.
We have studied density-dependent time-resolved photoluminescence from a 80 A InGaAs/GaAs single quantum well excited by picosecond pulses. We succeed in giving evidence for the transition from an exciton-dominated population to an unbound electron-hole pair population as the pair density increases. For pair densities below this excitonic Mott transition we observe a spectrally separate emission from free electron-hole pairs in addition to excitonic luminescence, thereby proving the coexistence of both species. Exciton binding energy and band gap remain unchanged even near the upper bound of this coexistence region. Above the Mott density we observe a purely exponential high energy tail of the photoluminescence and a redshift of the band gap with pair density. The transition occurs gradually between 1 x 10(10) and 1 x 10(11) cm(-2) at the carrier temperatures of our experiment.
我们研究了由皮秒脉冲激发的80埃铟镓砷/砷化镓单量子阱的密度依赖时间分辨光致发光。随着电子-空穴对密度的增加，我们成功地证明了从激子主导的粒子群体到未束缚电子-空穴对群体的转变。对于低于这种激子莫特转变的对密度，除了激子发光外，我们还观察到自由电子-空穴对的光谱分离发射，从而证明了这两种粒子的共存。即使在这个共存区域的上限附近，激子结合能和带隙也保持不变。在莫特密度以上，我们观察到光致发光的纯指数高能尾部以及带隙随对密度的红移。在我们实验的载流子温度下，转变在1×10¹⁰和1×10¹¹厘米⁻²之间逐渐发生。
