Near-infrared high-power LED's with Ga1-xAlxAs epitaxially grown junctions

This paper reports on a study of several techniques of fabricating an efficient Ga
1-x
Al
x
As IRED with high power. Smooth epitaxial layers are grown on a substrate containing a thick Ga
1-x
Al
x
As epitaxial layer which is used to form a hemispherical emitting surface. This is achieved by using a melting-back technique without up-heating. An effect of the AlAs molefraction ratio between n- and p-type regions was clearly found by measurement of a large number of diode chips, and the best performances were obtained on the junctions with the ratio
X_{n}/X_{p} \simeq 1.5
. Ohmic contacts to the p and n regions were applied on the same surface of the wafer using only one metallic source for the vacuum deposition. A cerium-oxide film serves as an antireflection coating when deposited on the hemispherical surface and increases the optical output power by more than 30 percent. External quantum efficiencies of 28 percent (current density: 400 A/ cm
²
) and optical output power of 96 mW (drive current: 300 mA, current density: 1500 A/cm
²
) have been observed from diodes emitting at 8300 Å under dc operation at room temperature.