B. Molnar

The Effect of Hydrogen-Based, High Density Plasma Etching on the Electronic Properties of Gallium Nitride

Development of devices based on the wide gap semiconductor gallium nitride (GaN) requires the realization of reliable, high fidelity, low damage pattern transfer processes. In this work, GaN thin films grown by OMVPE have been subjected to both chlorine- and methane/hydrogen-based etch chemistries in an electron cyclotron resonance microwave plasma reactive ion etching system. Both n-type and semi-insulating thin films have been utilized to examine the effect of these etch processes on the electronic properties of the materials. The methane/hydrogen-based etch system (CH{sub 4}/H{sub 2}/Ar) induced considerable changes in the electrical properties of both n-type and semi-insulating films, causing the former to become more insulating and the latter to become conducting. In both cases, the original electrical properties were recoverable after a short, high temperature anneal. In the chlorine-based etching system (Cl{sub 2}), no changes in the electrical properties were observed and etch rates five times greater than in the methane/hydrogen-based system were achieved. Proposed mechanism responsible for the observed behavior will be discussed. These results show that pattern transfer processes based in chlorine etch chemistries are more suitable for the generation of high performance GaN devices.

ION-IMPLANTATION IN SIC AND GAN

Abstract The electrical activation behavior of N- and Al-implantations in bulk V-doped semi-insulating 4H–SiC is similar to that in 4H–SiC epitaxial layers. The As- and Sb-implantations in p-type 6H–SiC epitaxial layers showed out-diffusion behavior with room-temperature sheet carrier concentrations of

Patterning of GaN by ion implantation-dependent etching

Abstract In earlier work we demonstrated that GaN can be selectively etched in the photoresist developer AZ-400K after ion implantation. Subsequent studies of etching solutions and etching bath temperature show the same etching behavior for KOH solutions and AZ-400K. Increasing etching bath temperatures increases the initial etch rate as well the final etching depth. Additionally the etching depth depends on the implantation parameters and increases with increasing ion dose and ion energy. The final etching depth can be correlated with the depth and degree of damage, induced by ion implantation. Patterning of GaN is possible by ion implantation through a mask followed by wet etching. Maskless patterning can be achieved with a focused ion beam.

Comparison of Isothermal Anneal Techniques for be or Si Implanted S.I. InP

This paper presents a study of the annealing of Be and Si implants into InP. It compares rapid thermal anneal (RTA) and furnace anneal (FA) techniques over a temperature range of 600-;900° C. The results demonstrate that RTA results in activation and mobilities as good as those obtained by FA for both Si and Be implant. The background Fe concentration of S.I. InP substrates lead to substantial differences in activation. Arrhenius fit of optimal activation data of Si indicates an activation energy of 1.8 eV. The Si implants display no redistribution during either type of annealing, while the Be implants display more than one type of redistribution. Moreover, the complete description of the Be redistribution requires the knowledge of both the atomic and the electronic profiles. Capless annealing eliminates the additional processing steps of capping but it also sets a limit on the maximum temperature and time of the annealing.

Wet Etching of Ion-implanted GaN Crystals by AZ-400K Photoresist

The photoresist developer AZ-400K, commonly used to remove AlN encapsulant layers on GaN crystalline films, is found to also etch certain as-grown GaN films. Even as-grown GaN films, which can not be etched in AZ-400K, however can be etched if amorphized by ion implantation. Etch rates of as high as 450 A/min. were observed. The etching proceeds linearly in GaN in the first few minutes to a depth corresponding to the depth of the amorphous region. Subsequently, the etching rate saturates. Annealing of the highly amorphized samples up to 1000°C for one minute in a N 2 /H 2 gas mixture does not reduce the etch rate, but for lower doses we observed a reduction of the etch rate. Observations of etching depth under various ion-implanted conditions could be correlated with the number of displacements per atoms (dpa) required for amorphization.