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We report on p-n junction light-emitting diodes fabricated from MgZnO / ZnO / AlGaN / GaN triple heterostructures. Energy band diagrams of the light-emitting diode structure incorporating piezoelectric and spontaneous polarization fields were simulated, revealing a strong hole confinement near the n-ZnO / p-AlGaN interface with a hole sheet density as large as 1.82 ϫ 10 13 cm −2 for strained structures. The measured current-voltage ͑IV͒ characteristics of the triple heterostructure p-n junctions have rectifying characteristics with a turn-on voltage of ϳ3.2 V. Electron-beam-induced current measurements confirmed the presence of a p-n junction located at the n-ZnO / p-AlGaN interface. Strong optical emission was observed at ϳ390 nm as expected for excitonic optical transitions in these structures. Experimental spectral dependence of the photocurrent confirmed the excitonic origin of the optical transition at 390 nm. Light emission was measured up to 650 K, providing additional confirmation of the excitonic nature of the optical transitions in the devices.

We report on the fabrication and characterization of solar blind photodetectors (SBPs) based on undoped β‐Ga2O3 and Zn doped (∼5 × 1020 cm−3) β‐Ga2O3 (ZnGaO) epitaxial films with cutoff wavelength of ∼260 nm. The epilayers were grown on c‐sapphire by the metal organic chemical vapor deposition technique and their structural, electrical and optical properties were characterized using various methods. As grown films have a large number of defects, resulting in detectors with enhanced internal gain, hence, high spectral responsivity >103 A/W. Post growth annealing in oxygen improved the quality of the epilayers, leading to detectors with reduced dark current (∼nA to ∼pA) and increased out of band rejection ratio. At 20 V bias, a ZnGaO detector showed a peak responsivity of 210 A/W (at 232 nm) and an out of band rejection ratio (i.e., R232 nm/R320 nm) of 5 × 104. Alternatively, for a β‐Ga2O3 detector these parameters were found to be five times and three times lower, respectively, suggesting that ZnGaO detectors have superior performance characteristics. These results provide a roadmap toward achieving high responsivity SBPs based on epitaxial ZnGaO films, laying a solid foundation for future applications.

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We report on the synthesis of Er-doped III–N double heterostructure light-emitting diodes (LEDs) and their electroluminescence (EL) properties. The device structures were grown through a combination of metalorganic chemical vapor deposition (MOCVD) and molecular-beam epitaxy (MBE) on c-plane sapphire substrates. The AlGaN layers, with an Al concentration of ∼12%, were prepared by MOCVD and doped with Si or Mg to achieve n- and p-type conductivity, respectively. The Er+O-doped GaN active region was grown by MBE and had a thickness of 50 nm. The Er concentration was estimated to be ∼1018 cm−3. The multilayer n-AlGaN/GaN:Er/p-AlGaN structures were processed into LEDs using standard etching and contacting methods. Several different LEDs were produced and EL spectra were recorded with both forward and reverse bias conditions. Typically, the EL under reverse bias was five to ten times more intense than that under forward bias. The LEDs displayed a number of narrow emission lines representative of the GaN:Er system (green: 539 nm, 559 nm; infrared: 1000 nm, 1530 nm). While some current crowding was observed, green emission was visible under ambient room conditions at 300 K. At cryogenic temperatures, the emission lines increased in intensity and had a narrower linewidth. EL spectra were recorded down to 10 K and the L-I characteristics were systematically measured. The power output of the brightest LEDs was approximately 2.5 W/m2 at 300 K.