Growth and characterization ofa-plane InGaN/GaN multiple quantum well LEDs grown onr-plane sapphire

Abstract

Non-polar a-plane InGaN/GaN multiple quantum well (MQW) light emitting diodes (LEDs) with different thicknesses and periods of InGaN wells are prepared and characterized. Non-polar a-plane LEDs are grown directly on r-plane sapphire by metalorganic chemical vapor deposition, and LEDs are fabricated. In the electroluminescence (EL) measurements, the relative output power increases slightly with increasing well thickness and the forward operating voltage at 20 mA increases slightly, even though the 4.2 nm thick well exhibits the best photoluminescence (PL) and x-ray diffraction (XRD) results. Although the interface quality degrades with thicker InGaN wells, the relative output power in EL measurement increases due to an increase of carrier capture rate with well thickness. With increasing periods of MQWs up to seven, the relative output power of LEDs is improved due to the increased crystal and interface quality in MQWs. Meanwhile, the forward operating voltage at 20 mA increases from 3.58 to 4.12 V because the series resistance of undoped areas increases with increasing periods of MQWs.

High indium non-polar InGaN clusters with infrared sensitivity grown by PAMBE

“…Non-polar (11)(12)(13)(14)(15)(16)(17)(18)(19)(20) a-plane InGaN epilayers were grown on 200nm GaN/Al 2 O 3 (1-102) substrate using an Omicron Nanotechnology plasma assisted molecular beam epitaxy (PAMBE) system. Sapphire substrates were first degreased using trichloroethylene, etched using H 2 SO 4 :H 3 PO 4 (3:1) at 150 0 C for 20 min and rinsed with deionized water before loading into the molecular-beam epitaxy chamber.…”

“…The Ga beam equivalent pressure (BEP) was kept at 5.6 x 10 −7 mbar, corresponding to the growth in the slightly nitrogen rich region. Following which, (11)(12)(13)(14)(15)(16)(17)(18)(19)(20) a-plane InGaN was grown at 550 0 C over the GaN epilayer for 2 hours in the same chamber. Nitrogen flow rate and RF power of nitrogen plasma were kept constant at 1 sccm and 350 watt respectively.…”

“…To overcome such polarization effect, substrates oriented in non-polar directions i.e. (10-10) m-plane or (11)(12)(13)(14)(15)(16)(17)(18)(19)(20) a-plane are used. Devices grown on these orientations are receiving a lot of focus due to this enhanced behavior; 7,8 however, a slight compromise in terms of quality has to be made because of the large in-plane mismatch between the lattice constants, thermal expansion coefficients and elastic constants of GaN and sapphire which leads to the generation of high densities of extended defects such as threading dislocations and basal plane stacking faults at the GaN-sapphire interface.…”

“…Song et al studied the effect of periodicity of a-plane InGaN/ GaN multiple quantum wells on the output power of the LEDs grown by MOCVD. 18 In our attempt to grow self assembled non-polar high indium InGaN quantum dots for the fabrication of high efficiency and bright LEDs operating in longer-wavelength regions, we have succeeded to grow non-polar high indium InGaN clusters of micron dimensions over non-polar (11)(12)(13)(14)(15)(16)(17)(18)(19)(20) a-plane InGaN epilayers grown on 200nm GaN/Al 2 O 3 (1-102) substrate. Detailed investigation of the structural and optical properties of the structure is undertaken in this work.…”

Heterostructures of III-Nitride Semiconductors for Optical and Electronic Applications

“…Few reports are available in the literature for the study of the nonpolar InGaN-based multiple quantum well (MQW) structures and other devices. Song et al studied the effect of periodicity of a-plane InGaN/GaN multiple quantum wells on the output power of the LEDs grown by MOCVD [71].…”