III-Nitride Short Period Superlattices for Deep UV Light Emitters

Sergey Nikishin

doi:10.3390/app8122362

Abstract

III-Nitride short period superlattices (SPSLs), whose period does not exceed ~2 nm (~8 monolayers), have a few unique properties allowing engineering of light-emitting devices emitting in deep UV range of wavelengths with significant reduction of dislocation density in the active layer. Such SPSLs can be grown using both molecular beam epitaxy and metal organic chemical vapor deposition approaches. Of the two growth methods, the former is discussed in more detail in this review. The electrical and optical properties of such SPSLs, as well as the design and fabrication of deep UV light-emitting devices based on these materials, are described and discussed.

Highlights

The invention of semiconductor double heterostructure laser [1,2] and the concept of a semiconductor superlattice (SL) [3] can be considered as the foundation of modern semiconductor p–n junction-based light emitters, lasers, and light-emitting diodes
The SLs based on the direct bandgap semiconductors in different combinations with p–n Double heterostructure (DHS) are used for design and fabrication of light emitters operating in very wide range of wavelengths, ensuring the needs of optical communication, medicine, security, lighting, and agriculture [4,5,6,7,8,9,10,11]
III-N light-emitting diodes (LEDs) based on very short period superlattices (SPSLs, sometimes referenced as digital alloys, DA), periodic structures of GaN/AlN, AlGaN/AlN, AlGaInN/AlN, InGaN/GaN, InN/GaN, and InAlN/GaN having a few monolayer thick wells and barriers, and a period not exceeding 2 nm, are very attractive for the design and fabrication of a new generation of light emitters

Summary

Introduction

The invention of semiconductor double heterostructure laser [1,2] and the concept of a semiconductor superlattice (SL) [3] can be considered as the foundation of modern semiconductor p–n junction-based light emitters, lasers, and light-emitting diodes. Under forward bias, the electrons and holes are injected from the cladding layers into an active layer, and well confined there Confinement of these injected carriers leads to very effective radiative recombination in direct bandgap semiconductors. The SL periodic layered structure of different crystalline semiconductors, allows for engineering of a bandgap of active (referred as a well) and cladding (referred as a barrier) layers when their thickness is of about a few nanometers. III-N LEDs based on very short period superlattices (SPSLs, sometimes referenced as digital alloys, DA), periodic structures of GaN/AlN, AlGaN/AlN, AlGaInN/AlN, InGaN/GaN, InN/GaN, and InAlN/GaN having a few monolayer thick wells and barriers, and a period not exceeding 2 nm, are very attractive for the design and fabrication of a new generation of light emitters. This review aims to summarize the most significant efforts demonstrated in this field since 2002, when the first LED based on AlGa(In)N/AlN SPSLs operating at 280 nm, was demonstrated [41,42]

Growth and Structural Characterization

O3 islands fromexposed

A forfor

Bandgap

Deep UV

Conclusions