MBE growth of AlN/GaN‐based photovoltaic intersubband photodetectors

Abstract

1 Introduction Intersubband (ISB) transitions in semiconductor quantum wells (QWs) have proven their capability for optoelectronics the mid-and far-infrared spectral regions. The extension of ISB optoelectronics towards the near infrared spectral region is interesting for the development of ultrafast photonic devices for optical telecommunication networks. Material systems with large enough conduction band offsets to accommodate ISB transitions at these relatively short wavelengths (1.3 µm, 1.55 µm) include InGaAs/AlAsSb, (CdS/ZnSe)/BeTe, and GaN/Al(Ga)N QWs. In the case of III-nitride heterostructures, their conduction-band offset − about 1.75 eV for the GaN/AlN system [1] − is large enough to develop ISB devices operating in the fibre-optics transmission windows at 1.3 µm and 1.55 µm. A specific advantage of III-nitrides is their extremely short ISB absorption recovery times (~150-400 fs [2]) due to the strong electron-phonon interaction in these materials, which open the way for devices operating in the 0.1-1 Tbit/s bit-rate regime. Furthermore, the remote lateral valleys lie very high in energy (>2 eV) above the Γ valley, which is a key feature to achieve ISB lasing. Finally, devices would profit from other advantages of nitride technology, such as high power handling capabilities and chemical and thermal robustness.In the last few years, various groups have reported ISB absorption at 1.3-1.55 µm in GaN/Al(Ga)N nanostructures in the form of QWs [1][2][3][4][5] or quantum dots [6]. The