Design of Terahertz Quantum Cascade Laser Sources

Abstract

newline THz quantum cascade-lasers (QCLs) are the best sources for generating efficient newlineTHz radiations, which are fabricated by the semiconductor heterostructure. The layers newlineof GaAs quantum wells and AlGaAs barriers are formed with different thicknesses to newlinedesign the heterostructure. There are many other sources to generate THz radiations newlinesuch as free electron lasers (FELs), femtosecond laser excited photoconductors, laser newlinedriven THz Emitters, photomixing sources etc. The study of devices to amplify the newlineterahertz (THz) radiations is a subject of intense research among the scientific commuand#65534;nity owing to the interdisciplinary applications. We explore the possibility of amplifi- newlinecation of THz radiations by investigating the transport measurements of GaN/AlGaN newlinestructures. We investigate the transport characteristics of AlGaN/GaN high-electronand#65534;mobility transistor (HEMT), transmission lines model (TLM), and interdigitated finger newline(IDF) structures as functions of geometry, temperature, and operating conditions. In newlinethe transport measurements of HEMT structure at 300 K, the pulsed mode operation newlineattains higher value of the drain current in comparison to the continuous wave opand#65534;eration mode of the relatively larger geometries which is typically related to the self newlineheating effect. Nevertheless, the pulsed mode operation transport measurements of newlinethe relatively smaller HEMT structures overlap and attain even lower drain current newlinevalues than that of the CW operation mode measurements whose origin is attributed newline8 newlineto the trap manifestation at low temperatures. The major part of the applied voltage newlineon the symmetric IDF structure is spread over the contacts whilst less than 10 % will newlineeffectively be applied on the channel