Semiconductors for terahertz photonics applications

Abstract

Abstract:Generation and measurement of ultrashort, sub-picosecond pulses of electromagnetic radiation with their characteristic Fourier spectra that reach far into terahertz (THz) frequency range has recently become a versatile tool of the far-infrared spectroscopy and imaging. This technique -THz time-domain spectroscopy, in addition to a femtosecond pulse laser, requires semiconductor components manufactured from materials with a short photoexcited carrier lifetime, high carrier mobility, and large dark resistivity. Here we will review most important developments in the field of investigation of such materials. Main characteristics of low-temperature-grown or ion-implanted GaAs and semiconducting compounds sensitive in the wavelength ranges around 1 µm and 1.5 µm will be surveyed. The second part of the paper is devoted to the effect of surface emission of THz transients from semiconductors illuminated by femtosecond laser pulses. Main physical mechanisms leading to this emission as well as their manifestation in various crystals will be described.

Quantum dot materials for terahertz generation applications

“…Thus GaAs PC devices incorporating QDs may offer the advantageous operating characteristics of semi-insulating (SI) GaAs while maintaining operating speeds comparable to LT-GaAs [16].…”

Terahertz emission from GaInAs p-i-n diodes photoexcited by femtosecond laser pulses

“…1(a). It is seen that the peak-to-peak amplitude of the pulse generated by the diode is ~75% larger than that obtained from the laser excited surface of the p-InAs single crystal, which was known up to now as the most efficient surface THz emitter [2]. The structure GaInAs-400 when excited with femtosecond 1030 nm wavelength pulses also showed larger than in the p-type InAs optical-to-THz conversion efficiency; only for the p-i-n structure with the thinnest i-region (GaInAs-200) this efficiency was smaller, but still comparable with the value of this parameter for p-InAs.…”

“…This type of THz radiation sources is a strong candidate for compact THz radiation systems powered by femtosecond fiber lasers with emission wavelengths between 1 and 1.55 μm because it does not require external biasing and materials with a large dark resistivity as it is in the case of photoconductive switches. Most efficiently THz pulses are radiated by femtosecond laser excited surfaces of the narrow gap semiconductors such as InAs [2]. This radiation originates either from nonlinear optical processes or ultrafast photocurrent transients.…”

Электрические и тепловые свойства фотопроводящих антенн на основе In-=SUB=-x-=/SUB=-Ga-=SUB=-1-x-=/SUB=-As (x>0.3) с метаморфным буферным слоем для генерации терагерцового излучения

“…Для увели-чения выхода ТГц сигнала требуется разрабатывать структуры с фотопроводящим слоем с малыми эффек-тивной массой и временем жизни фотовозбужденных носителей заряда [2,3]. В основном в качестве фото-проводящего слоя для ФА используют два материала: выращиваемый в низкотемпературном режиме GaAs (LT-GaAs) [4] и InGaAs [5]. Первый применяют для создания источников ТГц излучения под оптическую накачку фемтосекундного лазера (800 нм), а второй позволяет работать с более длинноволновой оптической накачкой в диапазоне 1.0−1.6 мкм [6,7].…”