GaN and InGaN quantum dots grown by MBE: from UV to red light emission

Nicolas Grandjean
Inst Pure Applied Physics, 2000
Conference paper

Group-III nitride quantum dots (QDs) are grown by molecular beam epitaxy. GaN/AIN QDs are used as a prototypical system for studying the interplay of the carrier localization and the built-in polarization field. The latter effect pushes the QD photoluminescence (PL) in the red range. InGaN/GaN QDs are fabricated taking advantage of the Stranski-Krastanow growth mode transition. In0.15Ga0.85N/GaN QDs exhibit a superior radiative efficiency compared to low In content (x less than or equal to0.1) InxGa1-xN/GaN quantum wells (QWs). However, the optical properties of InGaN/GaN QWs with an In composition of 20% are very close to those of In0.15Ga0.85N/GaN QDs. These similarities could be related to strong In composition fluctuations forming deep potential wells for x greater than or equal to0.15. Blue to red PL at room temperature is then observed on In0.2Ga0.8N/GaN QWs despite the huge density of dislocations. 0.4 to 0.6 mum electroluminescence is obtained from InGaN/GaN based light emitting diodes.

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Nicolas Grandjean
Inst Pure Applied Physics, 2000
Conference paper

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https://infoscience.epfl.ch/record/153176?ln=en

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Growth of gallium nitride epitaxial layers and applications

Nicolas Grandjean

The lack of appropriate substrates has delayed the realisation of devices based on III-nitrides. Currently, the heteroepitaxial growth of GaN by metal organic vapour phase epitaxy (MOVPE) produces GaN layers which, despite huge densities of dislocations, allow the fabrication of highly efficient optoelectronic devices. Henceforth, a new technology in heteroepitaxy of GaN, the epitaxial lateral overgrowth (ELO) has produced GaN layers in which the density of dislocations has been reduced by several orders of magnitude. With the ELO, nitride based laser diodes (LDs) working at room temperature in cw mode with a lifetime of 10,000 hours have been demonstrated by Nichia. In addition to LDs, III-nitrides presently offer a wide range of applications in optoelectronics (high brightness light emitting diodes (LEDs), from amber to UV, solar blind detectors); in electronics, high temperature/high power field effect transistors (FETs). The development of molecular beam epitaxy (MBE) of nitrides has been hindered during several years by the lack of an efficient nitrogen source. This problem being solved, MBE has recently demonstrated state-of-the-art quantum well and quantum dot heterostructures, and 2D electron gas heterostructures. (C) 2000 Academie des sciences/Editions scientifiques et medicales Elsevier SAS.

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Improved radiative efficiency using self-formed GaInN/GaN quantum dots grown by molecular beam epitaxy

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GaInN/GaN heterostructures have been grown by molecular beam epitaxy (MBE) on c-plane sapphire substrates. The growth of Ga1-xInxN (x > 12%) alloy has been extensively studied. At low V/III ratio, the growth undergoes a Stranski-Krastanov transition giving rise to the formation of three-dimensional (3D) islands. On the other hand, a high V/III ratio promotes the two-dimensional (2D) layer-by-layer growth regime. The optical properties of Ga1-xInxN (x > 12%)/GaN heterostructures made from either a 3D GaInN layer or a 2D GaInN layer are similar. This indicates that the mechanism responsible for the peculiar optical properties of Ga1-xInxN (x > 12%)/GaN heterostructures is intrinsically due to sell-formed quantum dots (QDs) that may arise from In clustering in the GaInN alloy. Actually, the properties of the GaInN/GaN QDs grown by MBE are very close to those grown by metal-organic chemical vapor deposition (MOCVD). As for MOCVD material, a high radiative efficiency is obtained correlatively with a giant Stokes shift and a very large carrier lifetime. The high efficiency of GaInN/GaN QDs is confirmed by gain measurements performed at room temperature. Finally, light-emitting diodes (LEDs) based on GaInN QDs have been fabricated. They demonstrate improved performances compared to LED based on homogeneous GaInN alloys.

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The growth of GaN layers was carried out on c-plane sapphire substrates by molecular beam epitaxy (MBE) using NH3. Undoped GaN layers were grown at 830 degrees C with growth rates larger than 1 mu m/h. Optical properties are characteristics of high quality GaN material and the linewidth of x-ray diffraction (0002) rocking curve is less than 350 arcsec. N-and p-type doping were achieved by using solid sources of Si and Mg. No post-growth annealing was needed to activate the Mg accepters. As-grown GaN:Mg layers exhibit hole concentrations of 3x10(17) cm(-3) and mobilities of 8 cm(2)/Vs at 300 K. Light emitting diodes (LEDs) based on GaN p-n homojunction have been processed. The turn on voltage is 3 V and the forward voltage is 3.7 V at 20 mA. The 300 K electroluminescence (EL) peaks at 390 nm.

Materials Research Society1998

Molecular-beam epitaxy

Molecular-beam epitaxy (MBE) is an epitaxy method for thin-film deposition of single crystals. MBE is widely used in the manufacture of semiconductor devices, including transistors, and it is consid

Light-emitting diode

A light-emitting diode (LED) is a semiconductor device that emits light when current flows through it. Electrons in the semiconductor recombine with electron holes, releasing energy in the form o

Gallium nitride

Gallium nitride () is a binary III/V direct bandgap semiconductor commonly used in blue light-emitting diodes since the 1990s. The compound is a very hard material that has a Wurtzite crystal structur