Entwicklung und Charakterisierung planarer Resonanz-Tunneldioden für den Einsatz in integrierten digitalen Schaltkreisen

In this work a planar technology for GaAs based resonant tunneling diodes is provided. These devices can be used in integrated digital logic circuits made from modular RTD/HEMT building blocks . In this way, an increased computational functionality can be achieved by extending the parallel processing capabilities an a gate level as an alternative to pure down-scaling of the minimum feature size. The starting point is the development of a self-aligned RTD process in which the diodes are defined by multiple ion implantation steps . A major question is if modern epitaxial growth and processing techniques can produce quantum devices like RTDs with a sufficient homogeneity for the application in robust digital circuitry. The analysis of about 300 diodes over a quarter of a 2-inch wafer Shows that a reliable operation of the designed gates can be expected. The impact of layer thickness variations in the tunneling structure is established by means of quantum transport simulations. As a result, the systematic part of the observed inhomogeneity can be attributed to a 2% decrease in the growth rate from the center of the wafer to the edge . This assumption is verified by photoluminescence measurements of quantum well structures . In order to demonstrate the potential of this concept, the integration of resonant tunneling diodes (RTDs) and enhancement-type high electron mobility transistors (E-HEMTs) to a logic NAND gate is presented exemplary. Again the emphasis is laid an the process technology and the electrical characterization of the single devices . PSpice simulations are employed to dimension the circuit in a way that the input and output levels of the gate are compatibl