GaAs/Al_(0.23)Ga_(0.77)As双量子阱的带边不连续性和阱间耦合

BAND-EDGE DISCONTINUITIES AND COUPLING BETWEEN WELLS FOR GaAs/Al_(0.23)Ga_(0.77)As DOUBLE QUANTUM WELLS

本文报道在300和77K对一组具有不同垒宽Lb的GaAs/Al_(0.23)Ga_(0.77)As双量子阱样品的光调制反射谱(PR)的研究结果。除观察到11H,11L和22H等容许跃迁外,同时还识别一个从Al_(0.23)Ga_(0.77)As价带顶至量子阱第一电子束缚能级的跃迁,另一个从量子阱第一轻空穴束缚能级至Al_(0.23)Ga_(0.77)As导带底的跃迁。利用这些跃迁确定导带边不连续性为0.63。对Lb≤40实验观察到11H和11L跃迁都明显地分裂成对称和反对称分量,对分裂大小的实验值与理论计算作了比较。在77K的11H的PR谱中在高能端明显地出现一个肩形峰,其形状不能用PR标准线形来拟合。如认为它对应于带间跃迁,并由此估计激子的束缚能约为8meV。

We report a detailed photoreflectance study at 300 and 77K of a set of GaAs/ Al0.23Ga0.77 As double quantum well samples with different barrier widths Lb. In addition to the allowed transitions of 11H, 1 1L and 22H,two other transitions have been also recognized as the transitions from the top of the Al0. 23Ga0.77As valence band to the first electron confined state and from the first light hole confined state to the bottom of the Al0.23Ga0.77As conduction band. By using these transitions the conduction band-edge discontinuity has been determined to be Qc = 0.63 + 0.02. For Lb<40A, we have observed a evident splitting of both transitions 11H and 11L into symmetrical and anti-symmetrical components. The experimental results of the splitting have been compared with theoretical calculations. A shouler-like peak at the higher energy side of the 11H transition, which can not be fitted by the standard PR line shape, was resolved at the 77K PR spectra. If he shoulder-like peak is assigned to be the band-to-band transition, we can determine the exciton binding energy to be approximately 8 meV.