Title :
Study of carrier dynamics in LT GaAs by means of time-resolved emission terahertz spectroscopy
Author :
Nemec, Hynek ; Kuzel, Petr ; Khazan, M. ; Schnull, S. ; Wilke, Ingrid
Author_Institution :
Inst. of Phys., Czechoslovak Acad. of Sci., Prague, Czech Republic
Abstract :
Summary form only given. Biased large aperture semiconductor emitters are widely used to generate ultrashort broadband terahertz (THz) pulses. The temporal shape of such pulses can be determined through a phase sensitive electro-optic or photoconduction sampling technique. The measured profile of the THz pulse then depends on several factors: (i) incoming optical pulse shape, (ii) dynamics of photo-excited carriers in the THz emitter, (iii) far-infrared optics transforming the THz beam, and (iv) receiving antenna or sensor spectral detectivity. We used 80 fs laser pulses at 800 nm generated by a self-mode-locked Ti:sapphire laser to excite biased GaAs samples. They consisted of a 1.3 /spl mu/m layer of MBE-GaAs grown at low temperatures (LT-GaAs) on a semi-insulating GaAs substrate with a 72.5 nm GaAs buffer layer. We studied several samples characterised by different deposition temperatures ranging between 175 and 250/spl deg/C. The irradiated THz waveform was measured using a ZnTe electro-optic sensor (without any focusing optics to avoid the waveform reshaping). The THz signal was studied as a function of several parameters (applied voltage, pump laser intensity, distance between biased electrodes). Lateral scans of the emitter position (with regard to the pump beam) were also performed.
Keywords :
III-V semiconductors; carrier lifetime; gallium arsenide; photoconductivity; semiconductor epitaxial layers; submillimetre wave generation; submillimetre wave spectra; time resolved spectra; 1.3 micron; 2.2 THz; 800 nm; GaAs; applied voltage dependence; biased large aperture semiconductor emitters; carrier dynamics; carrier lifetime; distance between biased electrodes; far-infrared optics; lateral scans; low temperature MBE samples; photo-excited carriers; photocurrent rise time; pump laser intensity dependence; semi-insulating substrate; temporal shape; time-resolved emission terahertz spectroscopy; ultrashort broadband terahertz pulses; Gallium arsenide; Laser excitation; Optical pulse generation; Optical pulse shaping; Optical sensors; Pulse measurements; Pulsed laser deposition; Shape measurement; Spectroscopy; Stimulated emission;
Conference_Titel :
Quantum Electronics Conference, 2000. Conference Digest. 2000 International
Conference_Location :
Nice, France
Print_ISBN :
0-7803-6318-3
DOI :
10.1109/IQEC.2000.908035