Extended wavelength photodiodes in the B-III–V material system

Abstract

Highly mismatched B-III–V alloys present a promising avenue for near-infrared (NIR), direct bandgap optoelectronics that can be integrated on GaAs or Si, owing to their ability to vary bandgap and lattice constant independently. Here, we report the epitaxial growth, fabrication, and characterization of nearly strain-free, all-BGaInAs, p-i-n photodiodes on GaAs substrates grown by molecular beam epitaxy. Incorporating boron effectively reduced the strain in InGaAs, yielding nearly lattice-matched BGaInAs layers with high surface quality, as confirmed by high-resolution x-ray diffraction and atomic force microscopy measurements. Strong photoluminescence (PL) intensity was observed for BGaInAs with up to 3.2% B (7% In). The operating wavelength consistently extended with increasing boron and indium incorporation as evidenced by PL and external quantum efficiency measurements, which agree with density functional theory predictions. Altogether, these results highlight precise control of the operating wavelength and suggest highly substitutional boron incorporation. BGaInAs photodiodes with low boron and indium concentrations demonstrated high sensitivity with low dark current. We also report the effective thermal conductivity of the BGaInAs p-i-n structures and find that the thermal conductivity is largely insensitive to boron content with dominant effects from the indium content. Altogether, these findings underscore the potential for strain-free BGaInAs photodiodes as promising candidates for high-performance NIR optoelectronics.