MBE growth of terahertz quantum cascade lasers

Details of the design, growth, fabrication, and operation of quantum cascade lasers (QCLs) that emit in the terahertz region (1-10 THz) of the electromagnetic spectrum are presented. Issues associated with the precision, stability, and uniformity of molecular beam epitaxy (MBE) growth conditions needed to achieve optimum device performance are discussed. Results from the very first terahertz QCL are shown, demonstrating the precision of the M BE growth. Next, the reproducibility of manufacture of the device is investigated. X-ray and emission spectra from repeat growths of the laser structure show excellent agreement between the intended design values and the actually grown samples. Device light-current characteristics show an improvement when the QCL is grown in progressively 'cleaner' regimes of the chamber's growth cycle. Finally, results from approximately 20 QCLs, comprising a variety of different active region designs, that emit over a large frequency range (2.4-4.7 THz, 125-64 μ m) with powers ranging from 0. 1 to 56 mW are reported. © 2005 Elsevier B.V. All rights reserved.