Thermal annealing and photoluminescence measurements on AlxGa1−xAs-GaAs quantum-well heterostructures with Se and Mg sheet doping

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Abstract
Transmission electron microscopy and photoluminescence data are presented, before and after sample thermal annealing, on AlxGa1−xAs‐GaAs quantum‐well heterostructures with Se or Mg sheet doping in the barriers or in the quantum wells (QWs). The crystals are grown by metalorganic chemical vapor deposition and, in the active regions, have four GaAs wells and three Al0.2Ga0.8As barriers (or in one case five QWs and four barriers). The confining layer regions are bulk doped n type on the substrate side and p type on top (p‐n). The sheet doping of the QW active region is obtained by deposition of Se from H2Se or Mg from bis(cyclopentadienyl) Mg in the middle of the layers (GaAs wells or Al0.2Ga0.8As barriers). The impurity sheet deposition (δ‐Se or δ‐Mg) is carried out in an arsine‐rich atmosphere. Photoluminescence data on the as‐grown crystals show that the energy (ℏω) of the recombination radiation is not shifted by the sheet doping and that the samples behave as ordinary photopumped QWH lasers. Annealing the crystals in an As4 atmosphere (provided by excess As in a quartz ampoule) causes layer intermixing of the Se sheet‐doped samples and very little disordering in the case of the Mg sheet‐doped samples. Magnesium sheet doping leads to layer disordering only in the case of sample annealing with no excess As in the annealing ampoule. Disordering of both Se and Mg sheet‐doped crystals occurs for Si3N4 capped but not for SiO2 capped samples.