Highly efficient THz emission from differently grown InN at 800 nm and 1060 nm excitation

A detailed study on differently molecular-beam epitaxy (MBE) grown InN wavers as THz surface emitters is reported. The samples were excited using 120 fs and 100 fs short laser pulses delivered by a Ti:Sapphire oscillator at 800 nm and a fiber laser amplifier at 1060 nm, respectively. The InN emission properties are compared to a p-type InAs reference sample. At 800 nm, atomically smooth InN with low background electron concentration exhibits slightly stronger THz emission than the well-established p-InAs emitter. This high THz efficiency of InN is reported for the first time. The strong emission of InN is caused by the absence of any intervalley scattering, which in the case of InAs, increases the effective mass of the photogenerated electrons and, thus, reduces the photo-Dember effect, which is most responsible for THz emission. Consequently, InN is a reliable material for strong THz emission.