We report the characteristics of InGaN multiple-quantum-well (MQW) green light-emitting diodes (LEDs) on Si (111) substrates. The MQW LEDs were grown on Si by metalorganic chemical vapor deposition using Al0.27Ga0.73N/AlN intermediate layers. The LED on Si showed an operating voltage of 7 V, a series resistance of 100 Ω, an optical output power of 20 μW, and a peak emission wavelength of 505 nm with a full width at half maximum of 33 nm at 20 mA drive current. The optical output power was half as compared to that of green LED on sapphire. The LED also exhibited a stable operation over 500 h under automatic current control (20 mA) condition at 27 °C.
The effect of Mn-doping into a GaN buffer layer grown by metal organic chemical vapor deposition (MOCVD) on the reduction in the leakage current of high-electron-mobility transistors (HEMTs) was investigated. Both the surface morphology and crystallinity maintained their quality even after heavy Mn-doping. The sheet resistance of GaN films increased with increasing amount of Mn-doping. The origin of semi-insulating GaN layer is considered to be electron scattering and the carrier compensation mechanism involving deep levels generated by the Mn impurity. When using the Mn-doped GaN buffer layer for the HEMT structure, the leakage current was reduced to five orders of magnitude lower than that without Mn-doping. Although Mn-doping is an effective technique for reducing the buffer leakage current, it is found that current collapse is emphasized when using the Mn-doped GaN buffer layer. We suggest that Mn atoms, which diffused to the GaN channel layer, induce the current collapse.
An intermediate layer consisting of AlN/AlGaN was used in the growth of InGaN multiple-quantum-well LEDs structure on Si(111) substrates. Crack-free films in 2 inch wafer and high-brightness LEDs were obtained. At 20 mA, the voltage is about 8.0 and 16.0 V for top and backside n-type electrodes, respectively. The EL peaks at $506 nm correspond to near band edge luminescence. The full width at half maximum of EL spectrum is 32 nm at 20 mA current. The output power is 23.0 and 19.4 mW at 20 mA for top and backside n-type electrodes, respectively. To our knowledge, this value is the best result of nitride LEDs grown on Si substrate even though it is less than the one on sapphire and SiC substrates.
A brief qualitative mapping is given between austenite, tweed and twinned phases of martensite alloys and corresponding paramagnetic, spin glass and periodic phases in spin glass alloys. This paper is dedicated to John Pendry in celebration of his 65th birthday.
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