Development of novel fabrication and simulation techniques for nanometer scale semiconductor photonic devices with application to nanophotodetector array.

摘要

The possibility to realize an array of photodetectors with nanometer or subwavelength scale is of great interest to various technologies. For example, with such a photodetector array, it will enable us to image objects at a resolution better than that of conventional diffraction-limited imaging tool. However, the realization of such a nanoscale photodetector (NPD) array is challenging and requires various innovative nanofabrication and simulation techniques. This dissertation focuses on the development of nanofabrication and simulation techniques for nanometer scale semiconductor photonic devices and demonstrated the application of some of these techniques to the realization of NPD array.;In this dissertation, first, a novel sub-10-nm nanolithography technique using sol-gel derived spin-coatable ZrO2 and TiO2 resists is presented. We then demonstrated their applications to semiconductor nanoscale direct patterning, where the smallest etching feature obtained is as small as 9 nm.;Second, to realize 3-dimensional fabrication that is essential to NPD array realization, a series of nanofabrication techniques are developed. They include: e-beam lithography for nanoscale metallization and device patterning; BCB wafer bonding and subsequent polish and etch back techniques; dry etching techniques for sub-10-nm scale patterning; development of transparent conductive oxide (TCO) material with high conductivity to optical loss ratio of 1.5 S.;Third, to simulate NPD array, which cannot be effectively performed by conventional FDTD method, a newly developed MLME FDTD model is applied to the simulation of photo detection by photodetectors. The optical coupling effect between NPD pixels is explored by varying the width of NPD pixels and their spacing.;Finally, the realization of novel NPD array is demonstrated by applying some of the newly developed fabrication techniques to NPD device. Both slab and channel version NPD array with up to 4x4 array size are successfully realized, where the smallest NPD pixel fabricated is 100 nm wide with 100 nm spacing. The NPD pixel shows a photocurrent of ∼135 nA at 3 V bias for 1310 nm wavelength light. The corresponding dark current is ∼1.25 nA, which is more than 100 times lower than the registered photocurrent.