Volume 88, Issue 4, 15 August 2000
Index of content:
- DEVICE PHYSICS (PACS 85)
88(2000); http://dx.doi.org/10.1063/1.1305838View Description Hide Description
Schottky barrierphotovoltaic detectors have been fabricated on and p-GaN epitaxial layers grown on sapphire. Their characteristics have been analyzed and modeled, in order to determine the physical mechanisms that limit their performance. The influence of material properties on device parameters is discussed. Our analysis considers front and back illumination and distinguishes between devicesfabricated on ideal high-quality material and state-of-the-art heteroepitaxial In the former case, low doping levels are advisable to achieve high responsivity and a sharp spectral cutoff. The epitaxial layer should be thin (<0.5 μm) to optimize the ultraviolet/visible contrast. In present devicesfabricated on heteroepitaxial the responsivity is limited by the diffusion length. In this case, thick layers are advisable, because the reduction in the dislocation density results in lower leakage currents, larger diffusion length, and higher responsivity. In order to improve bandwidth and responsivity, and to achieve good ohmic contacts, a moderate n-type doping level is recommended.
Theoretical consideration for carrier transport noise in nonequilibrium steady-state operation of metal–oxide–semiconductor field-effect transistor88(2000); http://dx.doi.org/10.1063/1.1305839View Description Hide Description
This article describes a theoretical approach to carrier-density-fluctuation-induced high-frequency transport noise in n-channel metal–oxide–semiconductor field-effect transistors(MOSFETs) under the condition of nonequilibrium steady-state operation. A partial differential equation describing the charge density fluctuation is formulated assuming the use of the current continuity condition. The model presented herein is applied to the analysis of the high-frequency transport noise in MOSFETs in a higher drain-to-source electric field range than is possible with the state-of-the-art model because the current continuity condition is taken into account. In contrast to the past result, it is shown that the normalized fluctuation power decreases or increases as the drain voltage increases, and it saturates at a certain value. When the drain voltage increases, the ratio of the carrier transit time to the effective relaxation time of fluctuation increases, which promotes the averaging of fluctuation. As a result, the increase in fluctuation is suppressed comparing with past theoretical results. In addition, the dependence of the carrier-density-fluctuation-induced transport noise on gate voltage is considered because both the local channel potential and the local carrier density inside the channel are taken into account in formulating the normalized fluctuation power. It is demonstrated that the normalized fluctuation power increases with gate voltage in the low gate voltage range and saturates at the certain value in the high gate voltage range. When the gate voltage increases, the ratio of the carrier transit time to the effective relaxation time of fluctuation decreases, which suppresses the averaging of fluctuation.