doped CdTe/Cdl-,Zn,Te quantum well heterostructures

Abstract: A comparative luminescence and magneto-transmission study is made of donor bound excitons DOX and negatively charged excitons X- in planar doped CdTeICdl-,&Te quantum wells of IWA width. AS the dopant plane is removed from the well centres to 450A distance in the barriers, DOX evolves continuously into an X- species weakly localised in random potential fluctuations. The exciton localisation energy in DOX transforms into the second electron's binding energy in X-. The use of precision planar doping techniques [I] allows accurate studies of impurity related and electron-gas related exciton transitions. In the previous conference in this series, we identified the donor bound exciton line DOX in CdTe/Cdl-,Zn,Te quantum wells planar doped with Indium donors ih the wells [2]. A more recent investigation of "modulation doped multi-QWs (that is QWs doped in the barriers) has led to the first clear observation of the negatively charged exciton line, X- (two electrons bound to one hole) [3]. The binding energy of the second electron of species X-, very low in 3D (only =0.05 Rydbergs), is dramatically increased in 2D [4]. The quantum confinement effect, together with the rather large CdTe Rydberg (14 meV), makes it relatively easy to observe X- in CdTe/Cdl-xZnxTe QWs. In the present paper we compare these two species, DOX and X-, studying the evolution of the DOX lin