Terahertz emission mechanisms in InAsxP1−x

Abstract

The terahertz emission mechanisms from the surface of bulk InAs x P 1−x crystals have been examined. The dominant terahertz emission mechanism from InAs x P 1−x for low-fluence optical excitation is the photo-Dember effect for As compositions of 78% and greater while the surface field effect is dominant for As compositions of 50% and lower for the measured transport properties. The observed terahertz emission magnitude from the photo-Dember effect increased with As composition due to decreasing absorption depth. The observed terahertz emission magnitude from the surface field effect decreased with increasing As composition and was lower than modeled values due to the lower high-field mobility in the depletion region in those samples.

Terahertz Emission Enhancement in InAs Thin Films Using a Silicon Lens Coupler

“…8,9) The nonlinear optical process is just the optical rectification of the pump laser at the semiconductor surface, 10,11) whereas, the current surge model can be explained by two types: the acceleration of photo-carriers through the surface depletion or accumulation field effect and the photo-Dember effect owing to the large difference in the mobility of electrons and holes. [12][13][14] Indium arsenide (InAs) is regarded as one of the best THz emitters of the bulk semiconductors for 800 nm laser excitation. 13) The reasons for the strong THz emission in InAs are due to the large carrier mobility ratio, small absorption length ($140 nm) and large excess energy of 1.2 eV (E 800 nm ¼ 1:55 eV, E gðInAsÞ ¼ 0:35 eV).…”