Intersubband transitions in nonpolar GaN/Al(Ga)N heterostructures in the short- and mid-wavelength infrared regions

Abstract

This paper assesses nonpolar m-and a-plane GaN/Al(Ga)N multi-quantum-wells grown on bulk GaN for intersubband optoelectronics in the short-and mid-wavelength infrared ranges. The characterization results are compared to those for reference samples grown on the polar c-plane, and are verified by self-consistent Schrödinger-Poisson calculations. The best results in terms of mosaicity, surface roughness, photoluminescence linewidth and intensity, as well as intersubband absorption are obtained from m-plane structures, which display room-temperature intersubband absorption in the range from 1.5 to 2.9 µm. Based on these results, a series of m-plane GaN/AlGaN multi-quantum-wells were designed to determine the accessible spectral range in the mid-infrared. These samples exhibit tunable room-temperature intersubband absorption from 4.0 to 5.8 µm, the long-wavelength limit being set by the absorption associated with the second order of the Reststrahlen band in the GaN substrates.2

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.…”

Effect of Al incorporation in nonpolar m -plane GaN/AlGaN multi-quantum-wells using plasma-assisted molecular-beam epitaxy

“…The substrates were free-standing m-GaN platelets sliced from (0001)-oriented GaN boules synthesized by hydride vapor phase epitaxy (resistivity > 10 6 V Á cm, dislocation density <5 Â 10 6 cm À2 ). For each design, growth was performed under the optimum conditions for c-GaN, i.e., slightly Ga-rich conditions [10,22,23], which are known to be compatible with m-plane growth [16,24]. The GaN wells were homogeneously doped with silicon, with the doping density indicated in Table 1.…”

“…We have previously reported that the (1-100) m-plane is the most promising nonpolar crystallographic orientation for ISB applications, based on comparative results with the (11)(12)(13)(14)(15)(16)(17)(18)(19)(20) a-plane [16]. By adjusting the Al mole fraction in the MQWs, ISB absorption in a broad range of the infrared spectrum was demonstrated.…”

“…By adjusting the Al mole fraction in the MQWs, ISB absorption in a broad range of the infrared spectrum was demonstrated. Near-and mid-infrared (MIR) ISB absorption in the 1.5-5.8 mm (826-214 meV) range has been observed on m-plane GaN/AlGaN MQWs [16,17] and photodetection at 7.5 and 9.3 mm (165 and 133 meV, respectively) has been demonstrated at 14 K using m-InGaN/(Al)GaN MQWs [18]. Low-temperature (T < 10 K) ISB absorption has been reported in the 3.77-10 THz (15.6-26.1 meV) window using nonpolar m-GaN/AlGaN MQWs [19,20].…”