Koji Okuno

m-Plane GaInN Light Emitting Diodes Grown on Patterned a-Plane Sapphire Substrates

The fabrication of a blue m-plane GaInN light emitting diode (LED) grown on an m-plane GaN layer grown on a 3-in. patterned sapphire substrate is reported. The output power of the LED was approximately 3 mW at the wavelength of 461 nm, a driving current of 20 mA, and a forward voltage of 3.5 V. This is the first report of nonpolar or semipolar blue LEDs grown on hetero-substrates with milliwatt scale output power.

m-Plane GaN Films Grown on Patterned a-Plane Sapphire Substrates with 3-inch Diameter

Nonpolar m-plane GaN films have been grown by metalorganic vapor-phase epitaxy on patterned a-plane sapphire substrates (diameter: 3 in.) without dielectric masks made of materials such as SiO2. The m-plane GaN layer had a smooth and transparent surface over the entire area of the substrate. Furthermore, the epitaxial relationships between the m-plane GaN film and the patterned a-plane sapphire substrate were as follows: [0001]GaN∥[0001]Sapphire and [1120]GaN∥[1010]Sapphire. The full width at half maximum values of the X-ray rocking curves for (1010) GaN along [1120]GaN and [0001]GaN were found to be 396 and 565 arcsec, respectively.

Growth Mode and Threading Dislocation Behavior of GaN Films Grown on Patterned Sapphire Substrate with Radial Stripe Pattern

A sapphire substrate with a grooved stripe pattern along different radial directions was prepared to investigate the effects of stripe direction on the growth mode and threading dislocation (TD) behavior of GaN films. When the stripe direction is oriented parallel to [100]sapphire, the GaN films have a triangular structure that is formed by the GaN{101} facets. As the stripe direction rotates from [100]sapphire, nanosteps with a step height of around 80 nm are formed on the GaN{101} facets and then the coalescence of GaN on the ridges and grooves advances. GaN films with a smooth surface and a TD density as low as 2.0×108 cm-2 were achieved when the stripe direction was rotated 3° from [100]sapphire. Our result indicates that the surface roughness and TD density of GaN films can be controlled by precisely adjusting the angle of the stripe direction from [100]sapphire.