Bandwidth of Integrated Photodiodes in Standard CMOS for CD/DVD application

his paper analyzes the bandwidth of high-speed photodiodes in a fully standard 0.18 μm CMOS technology for the CD/DVD optical pick-up units. Three diode structures are investigated: nwell/p-substrate, p+/nwell/p-substrate and p+/nwell. The photodiode performances are compared for λ = 780 nm and λ = 650 nm wavelength, corresponding to the lasers for CD and DVD, respectively. Slow substrate photocurrent component limits the bandwidth of nwell/p-substrate and p+/nwell/p-substrate photodiodes to 6 MHz and 7 MHz for a CD application as well as 70 MHz and 100 MHz for a DVD application. The third analyzed photodiode has bandwidth in the low GHz range for both applications, with the cost of at least 12 dB lower responsivity.