Hot phonons in InAs observed via picosecond free-carrier absorption

Abstract
The transient infrared absorption of hot electrons is studied in n-type InAs at a wavelength of 6.5 μm. The electron gas is heated by a picosecond infrared pulse to a maximum electron temperature of 560 K. The absorption of hot electrons exceeds the original value substantially and relaxes within 100 ps. Excess LO phonons created by the cooling process are important for the observed enhancement of free-carrier absorption. The free-carrier studies presented here give valuable information on the distribution function of hot phonons.