Abstract: Disclosed is an apparatus which can serve to detect, count, size discriminate and analyze the chemical composition of particles in the air or process gases. In a preferred embodiment, the particles enter via a capillary into a differentially pumped chamber. A pulsed laser which is continuously fired is focused at an opening in the chamber. When the particles come into the path of the laser beam, the particles are fragmented and ionized. A dual time of flight mass spectrum is produced, recorded with an oscilloscope and analyzed with a computer. The mass spectrum information enables the determination of the chemical nature and concentration of the species of the particles, the particle size and the elemental composition of airborne particles in real time. Once these parameters are determined the source of the particles can be determined and eliminated from the environment and process. Thus, the inventive apparatus is advantageously used in conjunction with a facility, i.e.

Abstract: It has been found that in the preparation of devices having repetitive layers, such as distributed Bragg reflectors, the dopant introduced during processing redistributes itself in a deleterious manner. In particular, this dopant through various effects segregates and diffuses from one layer into the interface region of the second layer. As a result, properties such as electrical resistance of the structure become unacceptably high. By utilizing various expedients such as carbon doping this segregation and its associated deleterious effects are avoided.

Abstract: This invention is concerned with the production of Schottky barrier gate contacts in MESFET devices. The contact is produced by wet-chemical removal of native oxide in a sealed inert gas ambient and blow-drying the wet-etched surface with the inert gas prior to deposition of gate electrode metal on GaAs by electron beam evaporation in an inert gas ambient. Use of Pt, due to its higher metal work function, as the gate contact metal results in a Schottky barrier height of 0.98 eV for Pt on n-type GaAs. This is considerably higher than the barrier height of conventionally processed TiPtAu contacts (0.78 eV).