Analysis of limitations of tetrahertz p-i-n uni-traveling-carrier photodiodes

The uni-traveling-carrier p-i-n photodiodes have been analyzed both in the ballistic and drift modes of operation. The analytical expressions for the tetrahertz (THz) power achievable with the photodiodes have been derived in the drift-diffusion approximation, the optimum photodiode parameters have been identified and different THz-power limitation mechanisms (space-charge effects, heating, absorption saturation, etc.) have been considered. It has been shown that the THz powers on the level of 300 mu W at greater than or similar to 1 THz, 10 mW at 0.3 THz and 30 mW at 0.1 THz should be achievable. That would give more than an order of magnitude improvement as compared to the present state-of-the-art results. At the lower end of the THz-frequency range, the main limitation mechanisms are the heating and space-charge effects. At the higher frequencies, at greater than or similar to 1 THz, the latter mechanism should play the major role. (C) 2007 American Institute of Physics.