InGaAsPN-InP-based photodetectors for long wavelength (/spl lambda/>1.65 μm) applications

We demonstrate InGaAsPN p-i-n photodetectors lattice-matched to InP substrates with cutoff wavelengths larger than 1.65 μm. The narrow bandgap InGaAsPN absorption layers were grown by gas source molecular beam epitaxy using an RF plasma nitrogen source. Optical absorption spectra reveal that InGaAsPN with 5% P and 2.8% N has a cutoff wavelength /spl lambda//sub CO/=1.90 μm Background doping in the absorption layer for a detector with 1.5% N and 5% P is reduced from (1.5/spl plusmn/0.5)×10/sup 17/ cm/sup -3/ for the as-grown device, to (5/spl plusmn/0.5)×10/sup 16/ cm/sup -3/ for a thermally annealed device. The unintentional high background doping is due to N-H bond formation or local strain induced defects. Spectral response measurements indicate that /spl lambda//sub CO/=1.85 μm is achieved for detectors annealed at 800/spl deg/C with 2% N and 5% P in the InGaAsPN absorption layer, suggesting that annealed InGaAsPN alloys are promising for use in detectors with response in the near and mid-IR wavelength spectral range.