Abstract

Photodetectors are needed for future communications systems utilizing novel mid-infrared fiber materials with extremely low predicted losses in the 2–4-μm wavelength range. We report improved performance of front-illuminated GalnAsSb/GaSb PIN homojunction photodiodes¹ that operate with high speed and high quantum efficiency at room temperature. The photodiodes consist of a Zn-diffused homojunction 0.3 μm below the surface of a 3-μm thick layer of n-type Ga_0.82ln_0.18As_0.17Sb_0.83. This layer was grown by liquid-phase epitaxy on a GaSb substrate and doped with Sn to a level of n = 2.5 × 10¹⁵cm⁻³. A partial metallization of the 100-μm diam mesa surface allows for front illumination of the chips, which are packaged as described in Ref. ². The external quantum efficiency without antireflection coating is constant at 55–65% for wavelengths up to 2.2 μm. At 1.06 μm the impulse response of the detector has a FWHM of 110 ps. At 1.3 μm it responds to pseudorandom modulation at bit rates up to 4 Gbit/s.

© 1986 Optical Society of America