Characteristics of Laser Diodes Composed of GaN-Based Semiconductor

Abstract

Violet laser diodes (LDs) with higher power and longer lifetime are required for some applications such as read/write laser light sources of digital versatile disks (DVDs). We achieved that the reliability of the LDs for DVDs was improved by using low dislocation density free standing GaN substrates. Moreover, we fabricated blue and ultraviolet (UV) LDs in order to spread the emission wavelength. The details of LD characteristics in the blue and UV region were investigated. In the blue LDs, there is a strong relationship between the threshold current density and the emission wavelength of LDs. For near UV LDs, we fabricated three types of LDs whose active layers are (I) ternary InGaN, (II) quaternary AlInGaN, (III) binary GaN single quantum well structures (SQW). We demonstrated the binary GaN SQW LDs under continuous-wave operation for the first time. From our experiments, we successfully expanded the range of GaN-based LDs emission wavelength, from UV (365 nm) to pure blue (465 nm).