Spontaneous interlevel emission from quantum dot and quantum well laser structures

The physical mechanism for creation of intraband population inversion between levels of quantum dots under injection of electron-hole pairs is suggested. The method is based on employment of generation of interband radiation providing fast depopulation of quantum dot ground level. Spontaneous far-infrared radiation (lambda approximate to 10...20 mu m) from diode laser structures with InGaAs/AlGaAs quantum dots connected with intraband hole and/or electron transitions between levels of size quantization in quantum dots was found and investigated for the first time. Spontaneous far-infrared radiation is observed only under simultaneous generation of stimulated near-infrared radiation (lambda approximate to 0.9 mu m) connected with interband carrier transitions. Far-infrared emission is observed also from laser structures with InGaAs/GaAs quantum wells. Intensity of this radiation is about of order less then intensity of radiation from structures with quantum dots. Qualitative explanations of phenomena observed are proposed.