Calibration of Polarization Fields and Electro-Optical Response of Group-III Nitride Based c-Plane Quantum-Well Heterostructures by Application of Electro-Modulation Techniques

Abstract

The polarization fields and electro-optical response of PIN-diodes based on nearly lattice-matched InGaN/GaN and InAlN/GaN double heterostructure quantum wells grown on (0001) sapphire substrates by metalorganic vapor phase epitaxy were experimentally quantified. Dependent on the indium content and the applied voltage, an intense near ultra-violet emission was observed from GaN (with fundamental energy gap Eg = 3.4 eV) in the electroluminescence (EL) spectra of the InGaN/GaN and InAlN/GaN PIN-diodes. In addition, in the electroreflectance (ER) spectra of the GaN barrier structure of InAlN/GaN diodes, the three valence-split bands, Γ9, Γ7+, and Γ7−, could selectively be excited by varying the applied AC voltage, which opens new possibilities for the fine adjustment of UV emission components in deep well/shallow barrier DHS. The internal polarization field Epol = 5.4 ± 1.6 MV/cm extracted from the ER spectra of the In0.21Al0.79N/GaN DHS is in excellent agreement with the literature value of capacitance-voltage measurements (CVM) Epol = 5.1 ± 0.8 MV/cm. The strength and direction of the polarization field Epol = −2.3 ± 0.3 MV/cm of the (0001) In0.055Ga0.945N/GaN DHS determined, under flat-barrier conditions, from the Franz-Keldysh oscillations (FKOs) of the electro-optically modulated field are also in agreement with the CVM results Epol = −1.2 ± 0.4 MV/cm. The (absolute) field strength is accordingly significantly higher than the Epol strength quantified in published literature by FKOs on a semipolar ( 11 2 ¯ 2 ) oriented In0.12Ga0.88N quantum well.

Engineering of Optical and Electrical Properties of Electrodeposited Highly Doped Al:ZnO and In:ZnO for Cost-Effective Photovoltaic Device Technology

“…Despite the fact that the principal techniques of optical characterization are spectroscopic ellipsometry and modulation spectroscopy (photo-and electro-reflectance of derivative nature and spectral shape) applied in Refs. [2,4,7,[9][10][11][12][13]33], the results of transmittance/reflectance measurements with the respective approximations refined in Refs. [78,79] have generally been proved highly useful.…”

“…Particularly, the wide band-gaps of AlN (6.2 eV), GaN (3.42 eV), and ZnO (3.37 eV) are favorable for high-power, short-wavelength light emitting devices [30][31][32]. Several optoelectronic applications of ZnO overlap with those of GaN, which is widely used for the production of green, blue-ultraviolet, and white light-emitting devices [33]. However, the interest in the ZnO research and applications has been facilitated due to its large exciton binding energy, paving the way for efficient room-temperature exciton based emitters, and its sharp optical transitions, enabling low-threshold laser diodes [28].…”