1. Field of the Invention
The present invention relates to a method of manufacturing a nitride semiconductor light emitting device suitably applicable to light emitting devices such as a light emitting diode (LED) or a laser diode (LD), a light receiving device such as a solar battery or an optical sensor, or to electronic devices such as a transistor or a power device.
2. Description of the Background Art
When an LED is used as an illuminating light source or a backlight for a display, it is necessary that the device has high light emitting efficiency and low forward voltage (hereinafter denoted as Vf). Japanese Patent Laying-Open No. 11-330554 discloses a nitride semiconductor light emitting diode having an active layer between an n-side nitride semiconductor layer and a p-side nitride semiconductor layer, allowing improved light emission output by providing an n-side multi-layered film layer formed of at least three layers including at least one first nitride semiconductor layer of undoped InxGa1-xN (0<x<1) and at least one second nitride semiconductor layer of undoped InyGa1-yN (0≦y<1, y<x) on an n-side contact layer, on which the n-electrode of n-side nitride semiconductor layer is formed.
The structure proposed in Japanese Patent Laying-Open No. 11-330554, however, has a tertiary mixed crystal of InGaN grown on the n-side contact layer, which may induce dislocation and defects in the crystal, possibly degrading light emission efficiency of the active layer. In a light emitting device such as an LD that operates with high current density, stacking an InGaN layer having narrower band gap than GaN or AlGaN may be a cause of overflow of introduced carriers. Therefore, there is a need for a technique that attains both high light emission output and low forward voltage (Vf).