Optoelectronic and Electrochemical Devices for Computing and Memory

Abstract

The Information Age exists in no small part thanks to the advent of complementary metal-oxide semiconductors (CMOS), which enable scaling of analog and digital circuits to the nanometer level. The devices built on this technology have enabled the gathering and processing of information from a variety of environmental sources. While silicon CMOS integrated circuits (ICs) still dominate in both computing and memory, new research is harnessing other materials and device architectures at the interface level in order to accomplish specific tasks. In the area of computing, deviation from the conventional von Neumann architecture, where processing and memory units are separated, is being explored–"in-memory" and "in-sensor" computing using new device designs offer a promising route to reducing latency, bandwidth, and power overhead. Furthermore, to keep up with staggering data demands, new memory architectures, such as those leveraging high density molecular systems, are also being investigated. Nonetheless, to expand past the research level, these systems must work synergistically with the scale of the mainstream silicon industry. This dissertation discusses the development of new optoelectronic and electrochemical devices for computing and memory that explores the interface between CMOS circuits and emerging architectures. First, an image sensor using an array of two-dimensional (2D) transition metal dichalcogenide (TMD) phototransistors heterogenously integrated on a CMOS readout IC is presented. This system demonstrates the largest scale fabrication of TMD devices (50x over state of the art) on a digital readout chip. Second, optoelectronic in-sensor computing is migrated from 2D materials to a scalable silicon platform–compatible with the CMOS foundry process–via an array of electrostatically doped p-i-n photodiodes built on an intrinsic silicon wafer. Third, building on recent works in molecular storage, a massively parallel, electrochemical CMOS IC containing 120,000 pixels, each comprising a set of concentric platinum microelectrodes and underlying driver circuits, is presented. It is then used for on-chip multiplexed DNA synthesis. Finally, the platform architecture is further scaled through a second generation IC that increases the number of reaction sites by an order of magnitude.