Improved speed performance of tensile-strained InxGa1-xAs (x<0.53) photodetectors utilizing a patterned substrate growth

Photodetectors (PDs) play an important role in optical communication systems and measurement systems. As the bandwidth of the optical communication system is increasing rapidly, high-speed PDs are needed. The mesa-type PDs such as Schottky and PIN-type PDs having InGaAs absorption layers are generally used for that field. The speed of those PDs in general is limited by hole transition time in the absorption layer. The speed performance limitation of mesa-type PDs due to the hole transition time can be improved by using a tensile-strained In_xGa_1-xAs (x<0.53) absorption layer. It was shown by simulations that the effective hole mass could be reduced by utilizing a tensile-strained In_xGa_1-xAs (x<0.53) absorption layer. Tensile-strained InAlAs/In_0.48Ga_0.52As and lattice-matched InAlAs/In_0.53Ga_0.47AS Schottky-type PDs were fabricated and characterized. Impulse response (FWHM) of the tensile-strained PD was reduced to 13 ps as compared with that (16 ps) of the lattice-matched PD, which is attributed to the improved hole transport property in the tensile-strained In_0.48Ga_0.52As absorption layer.