Optical gain in 1.3-μm electrically driven dilute nitride VCSOAs

We report the observation of room-temperature optical gain at 1.3 μm in electrically driven dilute nitride vertical cavity semiconductor optical amplifiers. The gain is calculated with respect to injected power for samples with and without a confinement aperture. At lower injected powers, a gain of almost 10 dB is observed in both samples. At injection powers over 5 nW, the gain is observed to decrease. For nearly all investigated power levels, the sample with confinement aperture gives slightly higher gain

AlGaN/GaN TEMELLİ YÜKSEK ELEKTRON HAREKETLİLİKLİ TRANSİSTÖRLERİN (HEMT) ELEKTRON VE MANYETO İLETİM ÖZELLİKLERİ

Bu çalısmada AlGaN/GaN ve AlGaN/AlN/GaN/AlN yapısına sahip 6 numunenin elektron iletim ve manyeto iletim özellikleri incelendi. Özdirençleri 22 – 350 K sıcaklığı arasında, Hall hareketliliği ve Hall tasıyıcı yoğunlukları aynı sıcaklık aralıklarında 0 – 1,5 T manyetik alan altında ölçülmüstür. Manyeto iletim sonuçları, Nicel Hareketlilik Spektrumu Analizi (QMSA) yöntemi kullanılarak analiz edilmis ve numunelerdeki 2-boyutlu ve 3-boyutlu iletim mekanizmaları birbirlerinden ayrıstırılmıstır. Hall ölçüm sonuçları ve QMSA ile ayrıstırılmıs 2-boyutlu iletim mekanizmasına ait sonuçlar ayrı ayrı saçılma analizlerinde ve katmanlar arası gerginlik hesabında kullanılmıs, aralarındaki fark irdelenmistir. Yapılan analizlerle, 2-boyutlu iletimin gerçeklestiği kuvantum kuyusunun genisliği, iletimin gerçeklestiği arayüzeyin bozukluğu ve gerginlikleri hesaplanmıstır. Yapısal özelliklere ait bu parametrelerin basarılı tayini, ileride elektriksel özellikleri daha iyi numunelerin üretilmesine yol gösterecektir.In this study, electron and magnetotransport properties of 6 different AlGaN/GaN and AlGaN/AlN/GaN/AlN structures were investigated. Resistivities were measured at a temperature range of 22 – 350 K, Hall mobilities and Hall carrier densities were measured at the same temperature range and magnetic fields between 0 – 1.5 T. Two-dimensional and 3- dimensional conduction mechanisms were seperated using Quantitative Mobility Spectrum Analysis (QMSA) of magnetotransport measurement results. Results of Hall measurements and QMSA results were used to conduct scattering analysis and strain calculations separately and the differences were examined. Well width of the quantum well that the 2-dimensional conduction occured, roughness of the related interface where the conduction occured and the strain of the interface were calculated. Succesfull calculation of these parameters related with the sctructural properties will lead to produce samples which will have better electrical properties

Energy Relaxation of Electrons in InGaN Quantum Wells

In this study, electron energy relaxation mechanisms in HEMT structures with different In x Ga1−x N-channel quantum well (QW) widths are investigated. Theoretical value of the inelastic scattering rates is carried out at electron temperatures between 30 K (−243 °C) < T e < 700 K (427 °C). We used both the experimentally determined and calculated electron temperatures to estimate the energy relaxation rates of non-equilibrium electrons. In wide InGaN QWs, power loss of an electron is shown to be significantly smaller than that in the narrower QWs

Temperature dependent energy relaxation time in AlGaN/AlN/GaN heterostructures

The two-dimensional (2D) electron energy relaxation in Al0.25Ga0.75N/AlN/GaN heterostructures was investigated experimentally by using two experimental techniques; Shubnikov-de Haas (SdH) effect and classical Hall Effect. The electron temperature (T-e) of hot electrons was obtained from the lattice temperature (T-L) and the applied electric field dependencies of the amplitude of SdH oscillations and Hall mobility. The experimental results for the electron temperature dependence of power loss are also compared with the current theoretical models for power loss in 2D semiconductors. The power loss that was determined from the SdH measurements indicates that the energy relaxation of electrons is due to acoustic phonon emission via unscreened piezoelectric interaction. In addition, the power loss from the electrons obtained from Hall mobility for electron temperatures in the range T-e > 100 K is associated with optical phonon emission. The temperature dependent energy relaxation time in Al0.25Ga0.75N/AlN/GaN heterostructures that was determined from the power loss data indicates that hot electrons relax spontaneously with MHz to THz emission with increasing temperatures. (c) 2012 Elsevier Ltd. All rights reserved

Temperature dependent energy relaxation time in AlGaN/AlN/GaN heterostructures

The two-dimensional (2D) electron energy relaxation in Al0.25Ga0.75N/AlN/GaN heterostructures was investigated experimentally by using two experimental techniques; Shubnikov-de Haas (SdH) effect and classical Hall Effect. The electron temperature (T-e) of hot electrons was obtained from the lattice temperature (T-L) and the applied electric field dependencies of the amplitude of SdH oscillations and Hall mobility. The experimental results for the electron temperature dependence of power loss are also compared with the current theoretical models for power loss in 2D semiconductors. The power loss that was determined from the SdH measurements indicates that the energy relaxation of electrons is due to acoustic phonon emission via unscreened piezoelectric interaction. In addition, the power loss from the electrons obtained from Hall mobility for electron temperatures in the range T-e > 100 K is associated with optical phonon emission. The temperature dependent energy relaxation time in Al0.25Ga0.75N/AlN/GaN heterostructures that was determined from the power loss data indicates that hot electrons relax spontaneously with MHz to THz emission with increasing temperatures. (c) 2012 Elsevier Ltd. All rights reserved

Negative Differential Resistance Observation and a New Fitting Model for Electron Drift Velocity in GaN-Based Heterostructures

The aim of this paper is an investigation of electric field-dependent drift velocity characteristics for Al0.3Ga0.7N/AlN/GaN heterostructures without and with in situ Si3N4 passivation. The nanosecond-pulsed currentvoltage (I-V) measurements were performed using a 20-ns applied pulse. Electron drift velocity depending on the electric field was obtained from the I -V measurements. Thesemeasurements showthat a reduction in peak electron velocity from 2.01 x 10(7) to 1.39 x 10(7) cm/s after in situ Si3N4 passivation. Also, negative differential resistance regime was observed which begins at lower fields with the implementation of in situ Si3N4 passivation. In our samples, the electric field dependence of drift velocitywas measured over 400 kV/cm due to smaller sample lengths. Then, a wellknown fitting model was fitted to our experimental results. This fitting model was improved in order to provide an adequate description of the field dependence of drift velocity. It gives reasonable agreement with the experimental drift velocity data up to 475 kV/cm of the electric field and could be used in the device simulators

SiC Substrate Effects on Electron Transport in the Epitaxial Graphene Layer

Hall effect measurements on epitaxial graphene (EG) on SiC substrate have been carried out as a function of temperature. The mobility and concentration of electrons within the two-dimensional electron gas (2DEG) at the EG layers and within the underlying SiC substrate are readily separated and characterized by the simple parallel conduction extraction method (SPCEM). Two electron carriers are identified in the EG/SiC sample: one high-mobility carrier (3493 cm(2)/Vs at 300 K) and one low-mobility carrier (1115 cm(2)/Vs at 300 K). The high mobility carrier can be assigned to the graphene layers. The second carrier has been assigned to the SiC substrate