Near-Infrared Absorption in Lattice-Matched AlInN/GaN and Strained AlGaN/GaN Heterostructures Grown by MBE on Low-Defect GaN Substrates

C. Edmunds, Purdue University
L. Tang, Purdue University
D. Li, Purdue University
M. Cervantes, Purdue University
G. Gardner, Birck Nanotechnology Center, Purdue University
T. Paskova, Kyma Technol Inc
Michael J. Manfra, Birck Nanotechnology Center, Purdue University
O. Malis, Purdue University

Date of this Version



Edmunds, C., Tang, L., Li, D. et al. Journal of Elec Materi (2012) 41: 881. doi:10.1007/s11664-011-1881-9


We have investigated near-infrared absorption and photocurrent in lattice-matched AlInN/GaN and strained AlGaN/GaN heterostructures grown by molecular-beam epitaxy (MBE) on low-defect GaN substrates for infrared device applications. The AlGaN/GaN heterostructures were grown under Ga-rich conditions at 745A degrees C. Material characterization via atomic force microscopy and high-resolution x-ray diffraction indicates that the AlGaN/GaN heterostructures have smooth and well-defined interfaces. A minimum full-width at half-maximum of 92 meV was obtained for the width of the intersubband absorption peak at 675 meV of a 13.7 GaN/27.5 Al0.47Ga0.53N superlattice. The variation of the intersubband absorption energy across a 1 cm x 1 cm wafer was +/- 1%. An AlGaN/GaN-based electromodulated absorption device and a quantum well infrared detector were also fabricated. Using electromodulated absorption spectroscopy, the full-width at half-maximum of the absorption peak was reduced by 33% compared with the direct absorption measurement. This demonstrates the suitability of the electromodulated absorption technique for determining the intrinsic width of intersubband transitions. The detector displayed a peak responsivity of 195 mu A/W at 614 meV (2.02 mu m) without bias. Optimal MBE growth conditions for lattice-matched AlInN on low-defect GaN substrates were also studied as a function of total metal flux and growth temperature. A maximum growth rate of 3.8 nm/min was achieved while maintaining a high level of material quality. Intersubband absorption in AlInN/GaN superlattices was observed at 430 meV with full-width at half-maximum of 142 meV. Theoretical calculations of the intersubband absorption energies were found to be in agreement with the experimental results for both AlGaN/GaN and AlInN/GaN heterostructures.


Nanoscience and Nanotechnology