Electronic measurements

The descriptions of practical works of computerized electronic measurements, carried out at the laboratory of measuring information systems of VGTU Electronics Faculty, are presented in the book. The objectives of the works are analyzed and the problems associated with the works, as well as methodical guidelines for carrying out practical works, and the requirements raised to work reports are presented. The review questions and self-work problems are also defined. The main part of the book is devoted to short descriptions of measurement instruments and computer programs used in the laboratory. The reader is familiarized with measurement instrument block diagrams, basic metrological specifications, and ways of instruments’ using and control. The book is intended for the students of the VGTU Electronics Faculty carrying out practical works in the laboratory of measuring information systems

Puslaidininkės medžiagos ultrasparčiajai optoelektronikai

The paper presents a review of experimental investigations of various semiconductor materials used for the development of ultrafast optoelectronic devices activated by femtosecond laser pulses that have been performed at the Optoelectronics Laboratory of the Semiconductor Physics Institute during the period from 1997 to 2008. Technology and physical characteristics of low-temperature-grown GaAs and GaBiAs layers as well as the effect of terahertz radiation from the femtosecond laser excited semiconductor surfaces are described and analysed.Lietuviška santrauka. Pateikta įvairių puslaidininkinių medžiagų, naudojamų kuriant ultrasparčius optoelektronikos prietaisus, žadinamus femtosekundiniais lazeriais, ekspwerimentinių tyrimų apžvalga. Tyrimai atlikti Puslaidininkių fizikos instituto Optoelektronikos laboratorijoje1997-2008 metais. Aprašyta žemoje temperatūroje augintų GaAs ir GaBiAssluoksnių technologija ir fizikinės savybės. Išsamiai aptyartas ir išanalizuotas THz spinduliuotės generavimas iš femtosekundiniu lazeriu sužadintų puslaidininkių paviršiaus

Low-Frequency Noise Investigation of 1.09 μm GaAsBi Laser Diodes

GaAsBi is a suitable and very attractive material system to be used as an active layer in laser diodes (LDs). To understand the performance and the reliability of such devices and also for further laser diode improvements, the origin of noise sources should be clarified. A detailed study of near-infrared 1.09 μm wavelength GaAsBi type-I laser diodes using the low-frequency noise spectroscopy in a temperature range of (180–300) K is presented. Different types of voltage fluctuation spectral density dependencies on the forward current far below the lasing threshold have been observed. According to this, investigated samples have been classified into two groups and two equivalent noise circuits with the corresponding voltage noise sources are presented. Calculations on the voltage spectral density of the electrical noise and current-voltage characteristic approximations have been performed and the results are consistent with the experimental data. The analysis showed that one group of LDs is characterized by 1/fα-type electrical fluctuations with one steep electrical bump in the electrical noise dependence on forward current, and the origin of these fluctuations is the surface leakage channel. The LDs of the other group have two bumps in the electrical noise dependence on current where the first bump is determined by overall LD defectiveness and the second bump by Bi-related defects in the active area of LD with characteristic Lorentzian-type fluctuations having the activation energy of (0.16–0.18) eV