The possible origins of the leaky characteristics of a Schottky barrier on p-GaN have been investigated. The as-grown samples did not show any electrical activity using Hall measurements. Ni diodes made on as-activated samples, either at 950/spl deg/C for 5 s or at 750/spl deg/C for 5 min exhibited quasiohmic behavior. Upon sequential etching of the sample to remove a surface layer of 150 /spl Aring/, 1200 /spl Aring/, and 5000 /spl Aring/ from the sample, the I-V behavior became rectifying. I-V-T measurements showed that the slopes of the lnI-V curves were independent of the temperature, indicative of a prominent component of carrier tunneling across the Schottky junction. C-V measurements at each etch-depth indicated a decreasing acceptor concentration from the surface. The highly doped (>1.7 /spl times/ 10/sup 19/ cm/sup -3/) and defective surface region (within the top 150 /spl Aring/ from surface) rendered the as-activated Schottky diodes quasiohmic in their I-V characteristics. The leaky I-V characteristics, often reported in the literature, were likely to originated from the surface layer, which gives rise to carrier tunneling across the Schottky barrier. This highly doped/defective surface region, however, can play an important role in ohmic contact formation on p-GaN.

The origins of leaky characteristics of Schottky diodes on p-GaN

An effective technique, which is based only on geometrical and physical data, is presented for the analysis of high-frequency FETs. The intrinsic part of this electron device is described by a quasi-two-dimensional hydrodynamic transport model, coupled to a numerical electromagnetic field time domain solver in three dimensions that analyzes the passive part of the FET. Such an analysis is entirely performed in the time domain, thus allowing linear and nonlinear operations. The obtained data give insights to some parameters affecting the signal distribution through the entire device structure; a comprehensive discussion of these is given for a test device. In order to prove the validity of the approach, the bias-dependent small-signal analysis is compared with the corresponding measurements up to 50 GHz for two 0.3-/spl mu/m gate-length AlGaAs-InGaAs-GaAs pseudomorphic high electron-mobility transistors, each having two gate fingers of 25-/spl mu/m and 100-/spl mu/m width, at bias points ranging from Idss to the pinchoff regime. The accuracy and the efficiency of the approach make it suitable for device optimization.

Physical/electromagnetic pHEMT modeling

This paper presents a coupled electrothermal, electromagnetic, and physical model for microwave power field-effect transistors (FETs). The resulting model is used to investigate large gate periphery pseudomorphic high electron-mobility transistor devices. The contribution to the output power of each cell of the transistor is simulated, as well as their contribution to the heating of the device. This approach allows the investigation of the interaction between the thermal behavior, the dc bias, and the microwave circuit operating conditions. This paper reveals for the first time a more complex interaction between the thermal and microwave behavior of large-power FETs

Coupled electrothermal, electromagnetic, and physical modeling of microwave power FETs

A comprehensive quasi-two-dimensional (Q-2-D) physical HEMT simulator is described for microwave CAD applications. It is used to accurately predict the DC and small-signal microwave performance of HEMT's. This simulator, which accounts for hot-electron effects in submicron HEMT's, includes parasitic MESFET conduction, quantum effects, and substrate injection phenomena. The accuracy of the present simulator is demonstrated by comparison with measured data for microwave HEMT's.

A quasi-two-dimensional HEMT model for DC and microwave simulation

A modified Poisson equation able to take into account the influence of gates and a ?-doping in FETs and HEMTs is proposed. This equation can be solved self-consistently together with 1D transport equations along inhomogeneous transistor channels like those of the hydrodynamic or drift-diffusion approximations or with a Monte Carlo simulator used to describe carrier transport in n+nn+ structures.

Pseudo-two-dimensional Poisson equation for the modeling of field-effect transistors

A new quasi-two-dimensional HEMT model has been developed that solves the physical device equations in a more rigorous fashion than previously reported. The model incorporates a quantum mechanical description of the free electron concentration, self-consistently solving the Schrodinger and Poisson equations. The influence of traps and incomplete donor ionization are also included. The conventional one-dimensional charge-control approach is shown to be inadequate for HEMT's and is replaced by a two-dimensional version that more accurately describes the channel dynamics under normal bias conditions. This allows the simulation to accurately model pinch-off characteristics, which are essential for digital, power and low-noise device characterization. The scheme also includes a detailed energy transport model, avalanche breakdown and gate conduction terms. The highly efficient model is applied to the DC and microwave characterization of AlGaAs-GaAs and pseudomorphic HEMT's. >

A quasi-two-dimensional HEMT model for microwave CAD applications

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A quasi-two-dimensional HEMT model for microwave CAD applications