Estimation of interwell terahertz gain by photon-assisted tunneling measurement in triple-barrier resonant tunneling diodes

Terahertz (THz) gain due to electron transition between adjacent quantum we lls was estimated from a measurement of current change in triple-barrier re sonant tunneling diodes under the THz irradiation. Measured current change was separated into stimulated emission and absorption components, and the g ain coefficient was estimated from the difference between these components. For a sample with relatively thick barriers and peak current density of 70 A/cm(2), the room-temperature peak gain coefficient was about 0.15 cm(-1) at 2.24 THz. The estimated gain coefficient is in reasonable agreement with an approximate theory. High gain is expected by increasing the current den sity with thin barriers. (C) 2000 American Institute of Physics. [S0003-695 1(00)02831-X].