Effect of doping on the far-infrared intersubband transitions in nonpolarm-plane GaN/AlGaN heterostructures

Abstract

This paper assesses the effects of Si doping on the properties of nonpolar m-plane GaN/AlGaN quantum wells (QWs) designed for intersubband (ISB) absorption in the far-infrared spectral range. For doping levels up to 3 × 10(12) cm(-2), structural analysis reveals uniform QWs with abrupt interfaces and no epitaxially induced defects. Cathodoluminescence spectroscopy confirms the homogeneity of the multiple QWs along the growth direction. Increasing the doping density in the QWs from 1 × 10(11) cm(-2) to 3 × 10(12) cm(-2) induces a broadening of the photoluminescence as well as a reduction of the exciton localization energy in the alloy. Also, enhancement of the ISB absorption is observed, along with a blue shift and widening of the absorption peak. The magnitude of the ISB absorption saturates for doping levels around 1 × 10(12) cm(-2), and the blue shift and broadening increase less than theoretically predicted for the samples with higher doping levels. This is explained by the presence of free carriers in the excited electron level due to the increase of the Fermi level energy.

Kinetic instability of AlGaN alloys during MBE growth under metal-rich conditions on m-plane GaN miscut towards the -c axis

“…To date, promising experimental results have been reported for near-and far-infrared intersubband absorption and photodetection in m-plane nitride heterostructures utilizing limited Al-composition alloys. [2][3][4][5][6][7][8][9][10][11][12] Mid-infrared intersubband absorption in m-plane AlGaN/GaN heterostructures grown by metal-organic chemical vapor deposition (MOCVD) was demonstrated by Kotani et al [4][5][6] We reported far-infrared (THz) intersubband absorption in AlGaN/GaN superlattices grown by molecular beam epitaxy (MBE). 2 Lim et al [7][8][9][10][11] also demonstrated short-to longwavelength infrared intersubband transitions in MBE-grown AlGaN/GaN heterostructures.…”

“…Nonpolar m-plane AlGaN/GaN heterostructures are interesting from both a fundamental material growth perspective and for practical applications in infrared optoelectronic devices. [1][2][3][4][5][6][7][8][9][10][11][12] Intersubband optoelectronic devices utilize optical transitions within the conduction band of GaN/AlGaN quantum wells to emit or detect infrared radiation. The accessible wavelength range is mainly determined by the conduction band-offset between the well and the barrier material, i.e., GaN and AlGaN in this case.…”

“…Lim et al also investigated the effect of Al-incorporation on the infrared optical properties of AlGaN/GaN m-plane multi-quantum wells, but no results were reported for Al composition between 45% and 99%. [7][8][9][10][11] Reports of Kotani et al are also limited to alloys below 50% Al composition, and did not contain any in depth structural analysis of the samples used in mid-infrared intersubband absorption measurements. [4][5][6] This paper concentrates on the defect structure of high Al-composition m-plane Al x Ga 1-x N/GaN (x > 0.5) superlattices.…”

Intersubband Transitions in Nonpolar m‐Plane AlGaN/GaN Heterostructures

“…Nonpolar nitride heterostructures have been proposed as alternative materials to polar heterostructures for infrared intersubband (ISB) devices . Due to large conduction band offsets between GaN and AlGaN, and large longitudinal‐optical phonon energy, the nitrides are potential candidates for near‐ to far‐infrared lasers and photodetectors.…”

“…We have made significant progress in growing m‐plane GaN and m‐plane AlGaN/GaN superlattices with Al‐composition below 20% that enabled us to observe THz intersubband absorption . Others have also had success growing m‐plane Al(Ga)N/GaN superlattices by different techniques in certain composition ranges . However, it remains challenging to control the Al content of m‐plane AlGaN over the full compositional range.…”