A partially depleted absorber photodiode with graded doping injection regions

A partially depleted absorber photodiode with graded absorption injection regions is reported. The 880-nm-thick In/sub 0.53/Ga/sub 0.47/As absorption region consists of a depletion layer and graded n- and p-type undepleted injection regions. Under backside illumination at 1.55-μm wavelength, an 8-μm-diameter photodiode exhibited an increase in bandwidth with increasing photocurrent. A saturation current bandwidth product of 990 mA /spl middot/ GHz and a responsivity of 0.67 A/W were achieved.