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Optical properties of InGaN/GaN multi-quantum-well (MQWs) grown on sapphire and on Si(111) are reported. The tensile strain in the MQW on Si is shown to be beneficial for indium incorporation and Quantum-confined Stark Effect reduction in the multi-quantum wells. Raman spectroscopy reveals compressive strains of -0.107% in MQW on sapphire and tensile strain of +0.088% in MQW on Si. Temperature-dependent photoluminescence shows in MQW on sapphire a strong (30 meV peak-to-peak) S-shaped wavelength shift with decreasing temperature (6 K to 300K), whereas MQW on Si luminescence wavelength is stable and red-shifts monotonically. Micro-photoluminescence mapping over 200 by 200 μm2 shows the emission wavelength spatial uniformity of MQW on Si is 2.6 times higher than MQW on sapphire, possibly due to a more uniform indium incorporation in the multi-quantum-wells as a result of the tensile strain in MQW on Si. A positive correlation between emission energy and intensity is observed in MQW on sapphire but not in those on Si. Despite the lower crystal quality of MQW on Si revealed by atomic force microscopy, it exhibits a higher internal quantum efficiency (IQE) than MQW on sapphire from 6 K to 250 K, and equalizes at 300 K. Overall, MQW on Si exhibits a high IQE, higher wavelength spatial uniformity and temperature stability, while providing a much more scalable platform than MQW on sapphire for next generation integrated photonics. 

Six periods of 2-nm-thick In0.15Ga0.85N/13-nm-thick GaN blue emitting multi-quantum-well (MQW) layers are grown on sapphire (Al2O3) and silicon (Si) substrates. X-ray diffraction, Raman spectroscopy, atomic force microscopy, temperature-dependent photoluminescence (PL), Micro-PL, and time-resolved PL are used to compare the structural and optical properties, and the carrier dynamics of the blue emitting active layers grown on Al2O3 and Si substrates. Indium clustering in the MQW layers is observed to be more pronounced on Al2O3 than those on Si as revealed through investigating band-filling effects of emission centers, S-shaped peak emission energy shifts with increasing temperature, and PL intensity-peak energy spatial nonuniformity correlations. The smaller indium clustering effects in MQW on Si are attributed to the residual tensile strain in the GaN buffer layer, which decreases the compressive strain and thus the piezoelectric polarization field in the InGaN quantum wells. Despite a 30% thinner total epitaxial thickness of 3.3 µm, MQW on Si exhibits a higher IQE than those on Al2O3 in terms of internal quantum efficiency (IQE) at temperatures below 250 K, and a similar IQE at 300 K (30% vs 33%). These results show that growth of blue emitting MQW layers on Si is a promising approach compared to those conventionally grown on Al2O3. 

Here we propose a new wide band gap logic circuitry providing emerging power electronics with reliable logic control capabilities with 500 MHz+ switching speeds and withstanding 300V+. Particularly, a three-stage ring oscillator composed of NMOS (μe = 1000 cm2/V-s) and PMOS (μh = 250 cm2/V-s) cubic phase GaN devices (with VT of 0.77 V and –0.84 V, respectively) is simulated. The propagation delay is minimized by optimizing the width-to-length ratio (W/L) between the NMOS and PMOS devices. Transient response of the simulation illustrates the ability of the CMOS inverter to operate at a maximum frequency of 1.22 GHz with a full voltage swing between VDD of 2.5 V and 0 V. The proposed cutting-edge p-channel GaN high hole mobility transistor (HHMT) solves one of the most longstanding problems in power electronics and constitutes the basis of an innovative reduced total life cycle cost that will serve as the cornerstone of the next generation of integrated, scalable, and reliable power systems.