Quantum cascade lasers grown on silicon

Abstract

Technological platforms offering efficient integration of III-V semiconductor lasers with silicon electronics are eagerly awaited by industry. The availability of optoelectronic circuits combining III-V light sources with Si-based photonic and electronic components in a single chip will enable, in particular, the development of ultra-compact spectroscopic systems for mass scale applications. The first circuits of such type were fabricated using heterogeneous integration of semiconductor lasers by bonding the III-V chips onto silicon substrates. Direct epitaxial growth of interband III-V laser diodes on silicon substrates has also been reported, whereas intersubband emitters grown on Si have not yet been demonstrated. We report the first quantum cascade lasers (QCLs) directly grown on a silicon substrate. These InAs/ AlSb QCLs grown on Si exhibit high performances, comparable with those of the devices fabricated on their native InAs substrate. The lasers emit near 11 µm, the longest emission wavelength of any laser integrated on Si. Given the wavelength range reachable with InAs/AlSb QCLs, these results open the way to the development of a wide variety of integrated sensors.The 20th Century has seen unparalleled success of the silicon-based microelectronics industry, whereas the 21st Century is witnessing the explosion of photonics. Silicon photonics lies at the convergence of both fields and promises to be the next disruptive technology for integrated circuits 1 . This however requires that the whole set of optoelectronics functions be integrated onto a Si platform. While various Si-based modulators and photodetectors have already been demonstrated 2-5 , integrated light sources have for long remained a challenge 6 . Silicon-based sources would straight away bridge the gap but the indirect bandgap of Si or Ge is a severe limitation and, in spite of unquestionable advances [7][8][9][10] , such devices will not outperform in the foreseeable future their III-V semiconductor counterparts which remain the most efficient semiconductor laser technology. Much work has thus been devoted in the last decade to integrating III-V laser diodes on Si platforms for telecom applications. Impressive results have been achieved in the visible to near infrared wavelength range by both heterogeneous integration, where III-V materials are bonded to silicon [11][12][13][14] , and direct epitaxial growth of III-V laser diodes on Si substrates [15][16][17][18][19][20] . In parallel, extending silicon photonics toward the mid-infrared (MIR) wavelength spectral region (2-20 µm) has emerged as a new frontier 21 . Indeed, most molecules exhibit absorption fingerprints in the MIR range 22 , which is of crucial interest for societal applications such as health diagnostics, detection of biological and organic compounds, monitoring of toxic gases or of greenhouse gas emission, to name but a few. MIR Si photonics could thus lead to integrated, compact, cost-effective, smart spectroscopy instruments 21,23 . Several groups have already demonstrated...