ABSTRACT It is very common that the driven voltage of the Light emitting diode device is around 1.8eV~2.2eV, however, in its applications the voltage that applied on the circuit is higher than this specification (3 eV as usual). It will be very annoying that the design of the LED circuit should always be in series with an extra resistor in order to protect the LED. In here we propose a method with a schottky contact structure on the device that we can solve this problem. Before we proceed this method, we had better fully understand the characteristics of the material physical properties , schottky contact and ohmic contact ,also include of the process of device. The substrate of the LED diode was chosen with N-GaP(111). The metal for the ohmic contact in this device is composed of Au/Au-Ge alloy. As to the schottky contact , the metal is formed by using Au element. The techniques for characterizing these contact properties include current-voltage (I-V), specific contact resistance (rc), ideal factor and current transport etc. The LED diode is also annealed at 450ºC for 10 minutes for improving the performance. The X-ray diffraction technique is applied to Investigate the interface of the contact area. The results of this experiment are summarized below: (I) The I-V curve of Ohmic contact is linear and contact resistance irc =7

Thesis (M.S. in Electrical Engineering)--Vanderbilt University, 2003. / Title from PDF title screen. Includes bibliographical references.

Zinc oxide is a II-VI semiconductor with considerable potential for optoelectronic and power-electronic applications in the UV spectrum, due to its wide direct band gap (3.35 eV at 300 K), high exciton binding energy (60 meV), high melting point, and excellent radiation hardness. A key requirement for many device applications is the consistent production of high performance Schottky contacts. Schottky contact formation to n-type ZnO was investigated via systematic studies into the relative performance of different metal and metal oxide Schottky contacts to hydrothermal and melt grown, bulk ZnO. The results of these studies can be explained by the dominating influence of two key mechanisms in the formation of high quality contacts: the removal of the natural hydroxide termination of ZnO and the associated surface accumulation layer, and the minimisation of process induced oxygen vacancies which tend to pin the barrier height of ZnO Schottky contacts in the 0.6 - 0.8 eV range. These investigations also led to the discovery of a new technique for the consistent production of high quality ZnO Schottky contacts, using the deposition of metal oxide films in reactive oxygen ambients. Specifically, silver oxide, iridium oxide, and platinum oxide films were used to consistently produce highly rectifying, very low ideality factor Schottky contacts to bulk ZnO, with figures of merit significantly better than those published in the literature. In addition, a number of previously unreported, surface polarity related effects were discovered in the electrical and optical properties of ZnO, which increase in magnitude with decreasing carrier concentration of the ZnO material. For example, metal oxide Schottky contacts fabricated on the Zn-polar surface of hydrothermal ZnO have significantly higher barrier heights than those on the O-polar surface, and low temperature (4 K) photoluminescence emission, from free excitons and excitons bound to ionised donors, is also significantly stronger from the Zn-polar face of the same material. These effects are thought to be related to the large spontaneous polarisation (-0.057 Cm-2) of ZnO, and indicate that surface polarity is an important variable when comparing experiment results with theoretical models, and in the future design of ZnO based devices.

No description available.

Thesis (M.S. )--Youngstown State University, 2007. / Includes bibliographical references (leaves 68-69).

Chemnitz, Techn. Univ., Diss., 2006.

Chemnitz, Techn. Univ., Diplomarb., 1997.

Darmstadt, Techn. Univ., Diss., 2004.

Universiẗat, Diss., 2005--Regensburg.

Ingeniero Civil Electricista / La generación de señales sinusoidales en el orden de las decenas y centenas de gigahertz van comúnmente asociadas con el uso de multiplicadores de frecuencia. En este contexto, el Laboratorio de Onda Milimétricas de la Universidad de Chile está interesado en adquirir el conocimiento necesario para construir estos dispositivos. El objetivo de esta memoria consiste en el diseño de un triplicador de frecuencia basado en diodos Schottky, cuya señal de entrada esté en el rango de frecuencia entre 30 a 40 GHz y su salida entre los 90 a 120 GHz. Se escogió para el diseño un triplicador basado en diodos Schottky del tipo resistivo, que entre sus características posee un gran ancho de banda operacional y buena estabilidad, pero una baja eficiencia. El diseño consiste en una conexión antiparalela de diodos, que entre otras ventajas, permite que no sea necesario polarizar el triplicador para que funcione, lo cual simplifica tanto el diseño de sus elementos como su implementación. Para validar el diseño obtenido, se hizo uso de dos programas de simulación. El primero corresponde a AWR Microwave Office, que permite hacer simulaciones no lineales mediante el método de balance de armónicas. El segundo es el programa Ansoft HFSS, que permite hacer simulaciones electromagnéticas a partir de la geometría del diseño. Solo mediante el uso de ambos programas se pudo obtener un diseño lo suficientemente robusto para justificar su construcción. Se logró diseñar un triplicador con una banda de multiplicación estable de 30 a 39,7 GHz, una eficiencia superior al 2% y una potencia de funcionamiento óptima de 17 dBm. Dada la baja eficiencia del triplicador (propio de este tipo de diseños), se sugiere la incorporación de un amplificador de potencia en su salida. Con los resultados obtenidos se valida la eficacia del método de diseño, por lo que puede ser utilizado como pauta para elementos de este tipo. Como trabajo futuro se propone estudiar el comportamiento térmico del triplicador e incorporar al diseño un disipador apropiado a sus requerimientos de temperatura, y una vez realizado esto, se propone la construcción del primer prototipo de diseño.