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For eventually providing terahertz science with compact and convenient devices,terahertz (1～10THz) quantum-well photodetectors and quantum-cascade lasers are investigated.The design and projected detector performance are presented together with experimental results for several test devices,all working at photon energies below and around optical phonons.Background limited infrared performance (BLIP) operations are observed for all samples (three in total),designed for different wavelengths.BLIP temperatures of 17,13,and 12K are achieved for peak detection frequencies of 9.7THz(31μm),5.4THz(56μm),and 3.2THz(93μm),respectively.A set of THz quantum-cascade lasers with identical device parameters except for doping concentration is studied.The δ-doping density for each period varies from 3.2×1010 to 4.8×1010cm-2.We observe that the lasing threshold current density increases monotonically with doping concentration.Moreover,the measurements for devices with different cavity lengths provide evidence that the free carrier absorption causes the waveguide loss also to increase monotonically.Interestingly the observed maximum lasing temperature is best at a doping density of 3.6×1010cm-2.
For eventually providing terahertz science with compact and convenient devices, terahertz (1 ~ 10 THz) quantum-well photodetectors and quantum-cascade lasers are investigated. The design and projected detector performance are presented together with experimental results for several test devices, all working at photon energies below and around optical phonons. Barkground limited infrared performance (BLIP) operations are observed for all samples (three in total), designed for different wavelengths. BLIP temperatures of 17,13 and 12K are achieved for peak detection frequencies of 9.7 THz 31 μm), 5.4 THz (56 μm), and 3.2 THz (93 μm), respectively. A set of THz quantum-cascade lasers with identical device parameters except for doping concentration is. The δ-doping density for each period varies from 3.2 × 10 10 to 4.8 × 1010 cm-2. We observe that the lasing threshold current density increases monotonically with doping concentration. More than that, the measurements for devices with different cavity lengths pro vide evidence that the free carrier absorption causes the waveguide loss also to increase monotonically.Interestingly the observed maximum lasing temperature is best at a doping density of 3.6 × 1010 cm-2.