1‐2 ML thick InN‐based quantum wells with InGaN barriers for blue‐green light emitters

Abstract

An LED structure with a 1‐2 monolayer (ML) thick InN quantum well (QW) with InGaN barrier grown by radio‐frequency plasma assisted molecular beam epitaxy (rf‐MBE) is proposed for a new active layer of blue‐green light emitters. Compared with previously reported 1‐2 ML thick InN/GaN QWs, extended emission wavelength up to pure green region (∼530 nm) is expected for these QWs with InGaN barriers. It is found that for the InN/InGaN QW structure, in which the InGaN layer is used as a barrier instead of GaN, very thin InN well layers are basically formed in the same manner as the InN/GaN QWs. In photoluminescence spectra at 15 K, emission peak wavelengths are observed from 412 nm to 480 nm when In contents in InGaN barriers are changed from 0.005 to 0.14. The emission wavelength is longer than that of 1‐2ML thick InN/GaN QWs (380nm‐430nm), and green emission can be obtained by further increase of In content in InGaN barrier to more than 0.2. The 1‐2 ML thick InN/In0.08Ga0.92N(10nm) 5‐QW LED structure was successfully fabricated and bright EL emission was observed at 419 nm, which is longer than that of a 1‐2 ML InN/GaN 5‐QW LED. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

InGaN/InGaN multiple-quantum-well grown on InGaN/GaN semi-bulk buffer for blue to cyan emission with improved optical emission and efficiency droop

“…This improved overlapping led to more radiative recombination and hence was consistent with the experimental increase of PL emission intensity [25]. For sample C, the spontaneous emission rate and the total radiative recombination rate (not shown here) were also calculated to be higher than that of the reference structures A and B, and was attributed to the reduced electric field [22,27]. This led to more homogenous distribution of carriers [20] in the MQWs grown on SB InGaN buffer and improved tunneling of electrons from the buffer that was un-intentionally n-doped and acted as an electron reservoir.…”

“…Several groups have proposed reduction of polarization field and improvement of optical performance by using semi-or non-polar direction growth [6][7][8], asymmetric QWs using AlGaN, InGaN, GaAsN [9][10][11], staggered QW [12][13][14][15][16], triangular QW [17][18][19], and using AlInGaN barriers [20]. Moreover, reduction or balance of strain has been suggested by using InGaN barrier [21][22][23], InGaN pre-layer [24][25][26][27][28] and also using In x Ga 1-x N/Al y Ga 1-y N/GaN MQW [29,30]; however, internal electric field might need to be sacrificed for improved material quality by strain compensation [29] and realization of a high quality InGaN buffer layer is also very critical, which has been addressed [26,31]. Nevertheless, good crystal quality, requirement of less In content to get same wavelength emission compared to that for semi-or non-polar direction growth [29] and mask free fewer processing steps make +c-direction growth still commercially promising and combined theoretical and experimental study to alleviate polarization field and enhance optical emission regarding this direction growth by optimized structure design are still important.…”

Analysis of InGaN-delta-InN quantum wells for light-emitting diodes

“…27-33͒ and molecular beam epitaxy ͑MBE͒. 26,[33][34][35][36][37] The growths of InN material by MBE have resulted in high electron mobility in the order of 2370 cm 2 / ͑V s͒. 34 The use of pulsed MOCVD has also resulted in high optical quality InN alloy.…”

“…27,28 Recent experimental studies by MBE have also indicated the capabilities to grow InN with monolayer precision. 26,37 The key idea from this work is to illustrate the advantage arises from the insertion of narrow-band gap delta-layer in InGaN QW, which enables the extension of emission wavelength while resulting in QW with large matrix element and large radiative recombination rate. Experimental studies are required to clarify on the optimized design for realistic InGaN-delta-InN QW LEDs, which require the need to take into account the large lattice mismatch and phase separation issues in InN/InGaN heterostructure, as well as current injection efficiency in nitride LEDs.…”

Performance of Nanostructures within InGaN-Based Multiquantum-Well Light-Emitting Devices

“…The improved performance of the light-emitting device can be attributed to the enhanced fluctuation in the overall indium composition of the sample with MQBs, which causes a stronger localization effect in the active layer and a better carrier spreading of the device [32]. Besides, with indium content in the barrier layer for the MQB sample, the polarization field in the well layer was reduced [23,33,34]. The reduced polarization field increases the electron-hole wave function overlap and results in a raised EL efficiency.…”