Терагерцевая генерация в эпитаксиальных пленках InAs

We present the results of terahertz generation studies under excitation via femtosecond lasers pulses epitaxial films of InAs, which were synthesized on semi-insulating and highly doped GaAs substrates. It is shown that a terahertz emitter based on epitaxial InAs film grown on a heavily doped GaAs n-type substrate, has the same terahertz generation efficiency as the InAs-film emitter grown on a semi-isolating GaAs substrate, but it has a significantly better spectral resolution, which is mainly determined by the parameters of the optical delay line and the femtosecond laser’s stability.

STUDY OF THE COMPOSITION OF GaAsBi FILMS OBTAINED BY PULSED LASER

Методом одноосного холодного прессования были изготовлены мишени GaAsBi с содержанием Bi 1 и 22%. Из полученных мишеней впервые было проведено импульсное лазерное напыления тонких пленок GaAsBi на подложках GaAs и Si. Были исследованы состав, спектры комбинационного рассеяния и фотолюминесценции тонких пленок GaAsBi, полученных из мишеней с содержанием Bi 1 и 22%. По данным спектров фотолюминесценции тонких пленок GaAsBi на подложках GaAs определено, максимальное содержание Bi в пленках не превышает 2,7 %. Полученные результаты хорошо коррелируют с результатами энергодисперсионного анализа, состав пленок, полученных из мишеней с содержанием Bi 1 и 22% - GaAs Bi и GaAsBi. Установлено, что фононная мода LO (GaBi). связанная с нарушением упорядоченности при смешении фаз GaAs и GaBi, находиться на частоте 181 см. Для тонкой пленки, полученной на подложке Si наблюдалась мода LO (GaAs), которая менее выражена и смещена на 3 см влево, в то время как запрещенная правилами отбора мода TO (GaAs) имеет более высокую интенсивность и ее смещение составляет около 1 см относительно частоты TO (GaAs) моды тонкой пленки, полученной на подложке GaAs . Uniaxial cold pressing was used to fabricate the GaAsBi targets with the Bi content of 1 and 22 %. From the obtained targets, pulsed laser deposition of GaAsBi thin films on the GaAs and Si substrates was carried out for the first time. We studied the composition, Raman and PL spectra of thin GaAsBi films obtained from targets with 1 and 22 % of Bi. According to the photoluminescence spectra of thin GaAsBi films on GaAs substrates, it was determined that the maximum content of Bi in the films did not exceed 2,7 %. The results obtained well correlate with the results of the energy dispersive analysis, the composition of films obtained from targets with the Bi content of 1 and 22% - GaAs Bi and GaAsBi. It was found that the LO(GaBi) phonon mode of associated with disordering during mixing of GaAs and GaBi phases to be at a frequency of 181 cm. For the thin film obtained on the Si substrate, the mode LO (GaAs) was observed that was less pronounced and shifted by 3 cm to the left, while the mode TO (GaAs), forbidden by the selection rules, had a higher intensity and its shift was of about 1 cm relative to the frequency of the mode TO (GaAs) of the thin film obtained on the GaAs substrate.

Electrical Properties of GaAs Implanted with High Energy (100meV) 28Si and 120Sn Ions

Single crystal n-GaAs substrates have been implanted at 300 K with 100 MeV 28Si and 120Sn ions to a dose of 1x1018ions/m2 independently. The electrical properties of these samples has been investigated and compared after implantation and annealing up to 850 °C by current voltage (I-V) measurements. It has been observed that the I-V curves for the samples implanted with 28Si ions show p-n junction like characteristics which then show a linear I-V characteristics for the annealing treatment between 150-550 °C. Annealing the samples at 650 °C results in a typical diode like I-V characteristics which become less non-linear after further annealing at 750 °C. Further annealing at 850 °C results in to a back ward diode like behavior. However the I-V curves for the samples implanted with 120Sn ions and annealed up to 450C were linear which then show a weak non linearity for the annealing treatments between 550C-750C. After 850C annealing the samples show a strong nonlinearity typical of a p-n junction. The temperature dependence of resistance of both 28Si and 120Sn implanted GaAs samples after implantation and different annealing steps are investigated and the possible conduction mechanisms are discussed.