Demonstration of polarization-induced hole conduction in composition-graded AlInN layers grown by metalorganic chemical vapor deposition

Abstract

This Letter reports the polarization induced hole conduction in composition-graded AlInN epitaxial layers grown by metalorganic chemical vapor deposition. First, the composition-graded AlInN layer with an InN mole fraction from 0.12 to 0.20 was formed on c-plane GaN on sapphire, and they were confirmed to show the p-type hole conduction with a less temperature dependence, which is a feature of polarization-induced carriers. Then, blue light-emitting diodes (LEDs) with the composition-graded AlInN layers inserted in the p-type side were fabricated and their vertical current injection was investigated. The electroluminescence (EL) spectra confirmed that the fabricated LEDs exhibited a single-peak blue-light emission with the help of the impurity Mg doping. The LED simulation indicated that the impurity and polarization co-doping effectively compensated and overcame the residual oxygen donors in the AlInN layer and promoted the carrier recombination at the light-emitting layers. Finally, LEDs with the Mg-doped and composition-graded AlInN insertion layer exhibited good current–voltage characteristics with a low forward voltage drop of approximately 3 V in addition to the good EL spectra.

Growth and Microstructure Analyses of Semipolar AlInN Epitaxial Layers on a Fully Relaxed Semipolar {112¯2} GaInN/GaN/m‐plane Sapphire Template

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Ternary AlInN alloys are viewed as useful component materials for GaN-based electronic and optical devices, such as barrier layers in heterostructure field-effect transistors (HFETs), [1,2] or cladding layers, [3,4] distributed Bragg reflectors (DBRs), [5,6] and active layers [7,8] in light-emitting devices. For the past several years, we have conducted intensive research on the epitaxial growth and characterization of c-plane AlInN layers with thicknesses of around 300 nm using metal-organic chemical vapor deposition (MOCVD), [9][10][11][12][13][14][15][16][17][18] as primarily aiming at their application to cladding layers in GaN-based visible laser diodes (LDs). Through those studies, we found the following thing.

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