The optical efficiency of GaN-based multiple quantum well (MQW) and light emitting diode (LED) structures grown on Si(111) substrates by metal-organic vapor phase epitaxy was measured and compared with equivalent structures on sapphire. The crystalline quality of the LED structures was comprehensively characterized using x-ray diffraction, atomic force microscopy, and plan-view transmission electron microscopy. A room temperature photoluminescence (PL) internal quantum efficiency (IQE) as high as 58% has been achieved in an InGaN/GaN MQW on Si, emitting at 460 nm. This is the highest reported PL-IQE of a c-plane GaN-based MQW on Si, and the radiative efficiency of this sample compares well with similar structures grown on sapphire. Processed LED devices on Si also show good electroluminescence (EL) performance, including a forward bias voltage of ∼3.5 V at 20 mA and a light output power of 1 mW at 45 mA from a 500×500 μm2 planar device without the use of any additional techniques to enhance the output coupling. The extraction efficiency of the LED devices was calculated, and the EL-IQE was then estimated to have a maximum value of 33% at a current density of 4 A cm−2, dropping to 30% at a current density of 40 A cm−2 for a planar LED device on Si emitting at 455 nm. The EL-IQE was clearly observed to increase as the structural quality of the material increased for devices on both sapphire and Si substrates.

Solution‐, vapor‐, and melt‐grown InP have been analyzed with photoluminescence measurements over the temperature range 5°–300°K. Although undoped material is discussed, the main emphasis is on doped InP grown from an indium solution for use as LED material. Optical activation energies were determined for hydrogenic donors, 7–10 meV; simple acceptors, zinc −50 meV, cadmium −58 meV, and mercury −98 meV; the isoelectronic trap bismuth, −31 meV; transition metal acceptors, copper −60–73 meV and manganese −270 meV.

An improved technique is described for the growth of InP by liquid-phase epitaxy. The use of gold-plated reflector tubes in the furnace design has improved the control of layer quality, and background doping levels have been consistently reduced to 3 X 10ZS/cm 3 by replacing polycrystalline InP by PH3(g) as a source of phosphorus. The behavior of the dopants S*~, Ge, S,i,, Te, Zn, Cd, and Bi in InP are discussed and the distribution coefficients "k' are found to be ksa --0.0019, kGe -"-0.005, ksi -"-4, kwe -" 0.27, kzn = 1.14, kcd _~ 0.002, km--0.002 to 0.0002The dopants Sn and Zn were found to be the most suitable for n and p doping for LED fabrication. The Group IV elements yielded n-type material only, although the mobility measurements indicated possible amphoteric behavior for Ge. The Hall mobilities at room temperature Ior the n-type samples show good agreement with theory.z Present address:

The issues and challenges of growing GaN-based structures on large area Si substrates have been studied. These include Si slip resulting from large temperature non-uniformities and cracking due to differential thermal expansion. Using an AlN nucleation layer in conjunction with an AlGaN buffer layer for stress management, and together with the interactive use of real time in-situ optical monitoring it was possible to realise flat, crack-free and uniform GaN and LED structures on 6-inch Si (111) substrates. The EL performance of processed LED devices was also studied on-wafer, giving good EL characteristics including a forward bias voltage of ~3.5 V at 20 mA from a 500 μm x 500 μm device.

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