Parameters Of High Electron Mobility Transistors Research Articles

Comparison of Two DC Extraction Methods for Mobility and Parasitic Resistances in a HEMT

The channel mobility, $\mu _{0}$ , parasitic source/drain resistances, ${R}_{S}/{R}_{D}$ , and virtual gate length, $\Delta $ , due to surface traps, at low drain–source bias, ${V}_{\text {DS}}$ , are important parameters of high-electron mobility transistors (HEMT’s). DC methods are available to extract these parameters from drain-current, ${I}_{D}$ , versus gate-source voltage, ${V}_{\text {GS}}$ , measurements. We report a comparative study of two such methods based on the linear ${I}_{D}-{V}_{\text {GS}}$ approximation, from the viewpoint of device modeling, process monitoring, and physical understanding. One method yields constant values of $\mu _{0}$ and ${R}_{S}+ {R}_{D}$ averaged over the ${V}_{\text {GS}}$ range, while the other yields variations of $\mu _{0}$ , ${R}_{S}$ , ${R}_{D}$ , and $\Delta $ with ${V}_{\text {GS}}$ . The study reveals some new details of these methods, and discusses their results on a range of GaAs and GaN HEMTs.

An extraction technique for small signal intrinsic parameters of HEMTs based on artificial neural networks

This paper presents a fast and accurate procedure for extraction of small signal intrinsic parameters of AlGaAs/GaAs high electron mobility transistors (HEMTs) using artificial neural network (ANN) techniques. The extraction procedure has been done in a wide range of frequencies and biases at various temperatures. Intrinsic parameters of HEMT are acquired using its values of common-source S-parameters. Two different ANN structures have been constructed in this work to extract the parameters, multi layer perceptron (MLP) and radial basis function (RBF) neural networks. These two kinds of ANNs are compared to each other in terms of accuracy, speed and memory usage. To validate the capability of the proposed method in small signal modeling of GaAs HEMTs, data and modeled values of S-parameters of a 200μm gate width 0.25μm GaAs HEMT are compared to each other and very good agreement between them is achieved up to 30GHz. The effect of bias, temperature and frequency conditions on the extracted parameters of HEMT has been investigated, and the obtained results match the theoretical expectations. The proposed model can be inserted to computer-aided design (CAD) tools in order to have an accurate and fast design, simulation and optimization of microwave circuits including GaAs HEMTs.

Impact of SF 6 plasma treatment on performance of AlGaN/GaN HEMT

Selective plasma treatment of an AlGaN/GaN heterostructure in the RF discharge of the electronegative SF 6 gas was studied. Shallow recess-gate etching of AlGaN (∼5 nm) was performed in CCl 4 plasma through a photoresist mask. Subsequently, recess-gate etching followed in situ by SF 6 plasma. The plasma treatment provides the following advantages in the technology of AlGaN/GaN high-electron mobility transistors (HEMT): It (1) simplifies their technology; (2) ensures sufficient selectivity; and (3) enables the technologist to set the threshold voltage of the HEMTs controllably. At the same time, the treatment can (1) provide the AlGaN/GaN heterostructure with surface passivation; (2) modify the 2DEG in any area of a HEMT channel; and (3) make it possible to convert a HEMT operation from depletion mode to enhancement mode. The treatment also improved significantly the DC and RF parameters of HEMTs studied.

A neural network approach for compact cryogenic modelling of HEMTs

This paper reports on a procedure based on the use of artificial neural networks (ANN) to fully model the performance of advanced high electron mobility transistors (HEMT) operating down to cryogenic temperatures. By means of this procedure, we reproduce the DC behaviour and the scattering (S-) parameters of the device under test (DUT). The I-V curves and the S-parameters of the DUT have been compared with measurements, and a good agreement has been found for assessing the capability of the ANN structure to predict the full behaviour of the DUT. Furthermore, we have analysed in detail the performance of two typical parameters of HEMT's, namely the transconductance and the output conductance. Their values have been derived from measured data and have been compared with those obtained by the ANN approach. Both the simulated DC and RF performance have shown an accuracy degree adequate to model the device properties down to cryogenic temperatures.

Characterization and performance of MOCVD grown 0.14-μm InP-HEMTs for low voltage applications

The layer structures of high electron mobility transistors (HEMTs) have been characterized by photoluminescence (PL), X-ray diffraction (XRD) and secondary ion mass spectrometry (SIMS) techniques. For the low voltage applications in mind, single and double delta-doped lattice matched HEMT devices have been processed and dc and RF performance is reported. At a drain-source bias of 1.25 V, a single delta doped 0.14-μm HEMT device shows an f T of 118 GHz and f max of 265 GHz. Similarly, a double delta doped 0.14 μm HEMT gives an f T of 135 GHz and f max of 140 GHz. The extracted physical parameters of HEMTs from PL and XRD techniques show excellent correlation with that of the grown devices.

Determination of HEMT's noise parameters versus temperature using two measurement methods

A simplified approach for the determination of the noise parameters of high electron-mobility transistors (HEMT's) at microwave frequencies has already been presented for devices tested at room temperature. Such method relies on the extraction of a noisy circuit model from measurements of the scattering parameters and the noise figure at the fixed source impedance of 50 /spl Omega/ (namely, F/sub 50/). The noise parameters of the device are then computed by model simulation. They exhibited a very good agreement with the noise parameters determined by the experimental procedure. In the present work, commercial pseudomorphic HEMT'S have been characterized at different temperatures in the 6 GHz to 18 GHz frequency range for validating the use of a further simplified procedure. We here show how to determine the complete noise performance of the devices from a very reduced set of measurements, i.e., the scattering parameters at each selected temperature and the F/sub 50/ noise figure at room temperature. The computed noise parameters are compared with those determined by application of the measurement procedure. The results show that the very simplified method can be employed with a good degree of accuracy whenever rapid noise testing of HEMT's versus temperature is needed.

Noise parameters of HEMTs: analysis of their properties from a circuit model approach

Noise parameters of high electron mobility transistors (HEMT) at microwave frequencies are a subject of active research since the knowledge of their performance is of key importance for the use of these devices for designing low‐noise amplifiers. Employs a simple noise model to derive the analytical expressions for the device noise parameters F0, Γ0 and N in terms of the electrical elements associated with the basic equivalent circuit of an HEMT. Analyses such expressions to establish some fundamental relationships, as well as the expected noise performance of the device when the parasitic elements representing package effects are included.