Multiple quantum-well intersubband devices for photodetectors and emitters

Intersubband transitions in both lattice-matched GaAs/AlGaAs and pseudomorphically strained GaAs/InGaAs/AlGaAs multi-quantum well structures are investigated. Absorption and emission devices were grown by atmospheric organometallic vapor phase epitaxy (OMVPE) and characterized using electroluminescence (EL) and Fourier transform (FT) spectroscopes. Several GaAs/AlGaAs quantum well infrared photodetectors infrared photodetectors (QWIPs) were fabricated and their performance evaluated. The dark currents and responsivities were measured and are found to be comparable to devices grown by advanced molecular beam epitaxial (MBE) methods. Significant improvements in the absorption characteristics were obtained by adopting a localized delta-doping profile in the absorption QWs as opposed to homogeneously doped structures. The measured absorption strength increased significantly in samples which were delta doped with silicon to sheet carrier densities of approximately {dollar}1times10sp{lcub}12{rcub}{dollar} cm{dollar}sp{lcub}-2{rcub}{dollar}. The transition linewidths decreased from 40 meV in the uniformly doped sample to 20 meV in the delta-doped devices. In addition, designs for intersubband emitters based on multiple quantum well structures are investigated. The electrical and optical properties of these devices are characterized. While no intersubband emission was observed from these device some possibilities for future designs are discussed.; Electrons injected into the excited subbands of SQW structures via a resonant tunneling mechanism was also investigated. The optical properties of light emitted from electron-hole recombination in the QW, characterized by electroluminescence spectroscopy, is correlated with the device electrical characteristics. At 77{dollar}spcirc{dollar} K both the I-V and the light attributes show strong nonlinear differential behavior similar to NDR effects in resonant tunneling diodes. Semiconductor laser diodes fabricated using these materials exhibit a single mode lasing spectrum and an output power characteristic which is abruptly extinguished as the field-induced resonant injection condition is exceeded.