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Fabrication of GaN/InGaN MQW blue light emitting diode G. Srivani Padma & Sumitra Singh & Manish Mathew & Kuldip Singh & B. C. Joshi & Surjit Das & C. Dhanavantri

Received: 17 July 2011 / Accepted: 11 July 2012 / Published online: 7 September 2012 # Optical Society of India 2012

Abstract GaN/InGaN Multiple Quantum Well LED structures were indigenously grown by MOCVD system on c-plane (0001) sapphire substrate. Blue LEDs at chip level were fabricated with various chip sizes. I-V characteristics were measured for the fabricated chips.

ranging from their roots as indicators and display signs to high-performance applications like automotive head lamps or projection systems [1]. Here we present the fabrication of GaN/InGaN Multiple Quantum Well Blue LEDs on indigenously grown epitaxial layers by MOCVD.

Keywords Electron Beam Evaporation . Multiple Quantum Wells . MOCVD . Photoluminescence . Reactive Ion Etching

Led structure

Introduction The III–V nitrides are large and direct energy gap semiconductors, which attract a lot of interest as optimum materials for short wavelength optoelectronic and high temperature electronic applications such as visible light-emitting diodes (LEDs), laser diodes, hetero-structure field effect transistors, and photodetectors. Light Emitting Diodes play a major role in the solid state lighting applications. Due to the enhancement in efficiency, reliability, low power consumption and long lifetime, LEDs were able to find their way into a wide field of applications G. S. Padma (*) : S. Singh : M. Mathew : K. Singh : B. C. Joshi : S. Das : C. Dhanavantri Optoelectronic Devices Group, Central Electronics Engineering Research Institute (CEERI), Pilani, 333031 Rajasthan, India e-mail: [email protected]

The LED structure consists of a nucleation layer of 30 nm grown at low temperature on c-plane sapphire substrate followed by a GaN buffer layer of 2000 nm, Si doped n-type GaN layer of 2000 nm, five pairs of InGaN QWs with a well width of 3 nm each and unintentionally doped GaN barrier width of 6 nm and Mg-doped p-type GaN layer of 100 nm. The epitaxial layers were grown by using MOCVD system. The grown LED structure is shown in Fig. 1. The growth conditions for the layers were reported earlier elsewhere [2]. P-type GaN activation was performed by using in-situ annealing in MOCVD system. The rms roughness value of as grown p-type GaN is about 0.17 nm measured by atomic force microscope. Photoluminescence (PL) measurement was performed by using RPM2000 (Accent, USA) on the epitaxially grown layers. PL spectrum for the epitaxial layers is shown in Fig. 2. It shows a peak emission wavelength at 450 nm which is well in blue region with a FWHM of 20.4 nm. The experimental and simulated rocking curves were

J Opt (October–December 2012) 41(4):198–200

199

Fig. 1 Schematic of LED structure Fig. 3 Schematic of fabricated planar LED chip

correlated for GaN/InGaN LED structure with five MQWs by using High Resolution X-Ray Diffraction (HRXRD) [3].

Fabrication LEDs of different l