Room temperature near-infrared intersubband transitions were observed in MBE grown non-polar cubic GaN/AlN superlattice structures. The peak wavelengths of these transitions were observed in the spectral region of 1.5–2.0 μm and were theoretically supported using a transfer matrix approach. All samples were unintentionally doped and grown on 3C-SiC substrates with a 100 nm GaN buffer. Each structure consisted of a 20 periods of GaN/AlN superlattice capped with 100nm of GaN. The thickness of the AlN barrier was fixed at 1.35, while the thickness of the GaN well was varied between 1.6 and 2.1nm. Electrochemical Capacitance Voltage (ECV) measurements allowed direct measurement of the intrinsic carrier concentration in a thick unintentionally doped cubic GaN layer, which confirmed sufficient population of the ground state energy level.

The interband and intersubband transitions in self-assembled InAs and In0.3Ga0.7As quantum dots grown by molecular beam epitaxy have been investigated for their use in visible, near-, and mid-infrared detection applications. Devices based on InAs quantum dots embedded in an InxGa1−xAs (0 to 0.3) graded well and In0.3Ga0.7As quantum dots were fabricated in order to measure the temperature dependent (77 – 300 K) photoresponse. The dark current was measured in the temperature range of 77 to 300 K for the devices. Room temperature photoresponse ranging between 0.6 to 1.3 μm was observed for the InAs and In0.3Ga0.7As quantum dot photodetectors. Furthermore, a dual band photoresponse in the visible, near-, and mid-infrared spectral regions for both devices was observed at 77 K. Using a self-consistent solution of Schrödinger-Poisson equations, the peak position energies of the interband and intersubband transitions in the two multi-color quantum dot infrared photodetector structures was calculated.

Intersubband transitions in the spectral range of 1.37-2.90 °Cm is observed in molecular beam epitaxy grown Si-doped GaN/AlN multiple quantum wells using a Fourier-transform spectroscopy technique. A blue shift in the peak position of the intersubband transition is observed as the well width is decreased. A sample with a well width in the order of 2.4 nm exhibited the presence of three bound states in the GaN well. The bound state energy levels are calculated using a transfer matrix method. An electrochemical capacitance voltage technique is used to obtain the three dimensional carrier concentrations in these samples which further enable the calculation of the Fermi energy level position. Devices fabricated from these GaN/AlN quantum wells are found to operate in the photovoltaic mode.