HEMT Layers Research Articles

Simplified assessment of parallel conduction in modulation-doped heterostructures

A technique for improving the accuracy of Hall-effect measurements on (Al,Ga)As/GaAs and pseudomorphic (Al,Ga)As/(In,Ga)As/GaAs HEMT layers and related structures in the presence of parallel conduction is proposed. It is based on an approximation to the standard 'two-band' model of parallel conduction, and allows an estimate of the degree of parasitic conduction present in the structure to be made simply by performing one additional measurement, namely that of the resistivity of the sample at the same magnetic field as is used for the Hall measurement. Correction factors can then be applied to the measured carrier density and mobility to give significantly improved values for these parameters in the two-dimensional electron gas region of the sample. Application of this technique to two typical experimental situations is then described.

Layer uniformity in a multiwafer MOVPE reactor for III–V compounds

New experimental results on the layer uniformity in the radial flow planetary MOVPE reactor geometry are presented. This reactor is capable of growing Ga 1- x Al x As on GaAs and lattice matched Ga 1- x In x As on InP on seven 2 inch wafers with a typical variation in thickness and doping of ±1% on each wafer and ±1% between the wafers of each run. The In percentage has a variation in a range of typically 0.05% on a wafer and less than 0.05% between the wafers. A theoretical and experimental study demonstrates how to avoid increased layer thickness near the edge of the wafers. The emissiion energies of strained Ga 0.82In 0.18As quantum wells on seven wafers, measured on several points per wafer, were found to be within a range of 8 meV. Results on HEMT devices and pseudomorphic HEMT layers are presented.

Low-noise high electron mobility transistors for monolithic microwave integrated circuits

High electron mobility transistors (HEMT's) for monolithic microwave integrated circuits have been fabricated that have demonstrated excellent performance. External transconductance of 300 mS/mm is observed and noise figures of 1 and 1.8 dB with associated gains of 16.1 and 11.3 dB at 8 and 18 GHz, respectively, have been measured. These are comparable to the best reported noise figures for either HEMT's or MESFET's and are the highest associated gains reported for such low-noise figures. Analysis of these devices indicates that further improvements in these results is possible through optimization of HEMT layers and fabrication technology to reduce gate-source parasitic resistance.

The trials of wafer-scale integration : Jack F. McDonald, Edwin H. Rogers, Kenneth Rose and Andrew J. Steckl. IEEE Spectrum 32 (October 1984)

Stacked layer sequences of InP-based HBT and HEMT are of interest for today's (OC-768) and tomorrows (OC-3072, 100 Gbit Ethernet) communication standards. The better low noise performance of the HEMT can be combined with the driver capability of the HBT while also a PIN-photodiode can be provided by the HBT base-collector-diode. However this results in a complex procedure for MOVPE growth process development. For a reliable fabrication of complex radio frequency (opto-)electronic circuit applications a quantitative InP process technology control is necessary starting at the level of device epilayer stacks. In this report the detailed characterization of stacked InP/(InGa)As:C HBT and InP/(InGa)As HEMT layer sequences is carried out by non-destructive X-ray analysis. Based on X-ray measurements in 004- and 002-reflection a detailed analysis of complex device layer stacks is purposed. As a result, an automatic calculation of layer parameters, e.g. thickness and composition is possible, reducing the turn-around time for the statistical process control (SPC).

Improving bond yields to metal package leads : Doug Day. Semiconductor Int. 90 (July 1984)

Stacked layer sequences of InP-based HBT and HEMT are of interest for today's (OC-768) and tomorrows (OC-3072, 100 Gbit Ethernet) communication standards. The better low noise performance of the HEMT can be combined with the driver capability of the HBT while also a PIN-photodiode can be provided by the HBT base-collector-diode. However this results in a complex procedure for MOVPE growth process development. For a reliable fabrication of complex radio frequency (opto-)electronic circuit applications a quantitative InP process technology control is necessary starting at the level of device epilayer stacks. In this report the detailed characterization of stacked InP/(InGa)As:C HBT and InP/(InGa)As HEMT layer sequences is carried out by non-destructive X-ray analysis. Based on X-ray measurements in 004- and 002-reflection a detailed analysis of complex device layer stacks is purposed. As a result, an automatic calculation of layer parameters, e.g. thickness and composition is possible, reducing the turn-around time for the statistical process control (SPC).