InGaAsPN-InP-based photodetectors for long wavelength (λ > 1.65 μm) applications

We demonstrate InGaAsPN p-i-n photodetectors lattice-matched to InP substrates with cutoff wavelengths larger than 1.65 mu m 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 lambda(CO) = 1.90 mu m. Background doping in the absorption layer for a detector with 1,5% N and 5% P is reduced from (1.5 +/- 0.5) x 10(17) cm(-3) for the as-grown device, to (5 +/- 0.5) x 10(16) cm(-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 lambda(CO) = 1.85 mu m is achieved for detectors annealed at 800 degrees 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.