Three dimensional heteroepitaxy: A new path for monolithically integrating mismatched materials with silicon

Abstract

In the quest for a Ge x-ray detector monolithically integrated onto a Si-CMOS chip we developed a novel method for combining dissimilar materials that may provide a solution to the main problems of heteroepitaxy, e.g. high threading dislocation densities, wafer bowing and cracks. It consists of replacing the conventional continuous layers by space-filling arrays of strain-and defect-free Ge crystals, the width, height and shape of which are controlled by tuning epitaxial growth onto micrometer-sized features deeply etched into Si-substrates. Heterojunctions formed between the Ge-crystals and the Si-substrate exhibit the required rectifying diode behavior with low dark currents (<1 mA/cm 2 ).

Individual heterojunctions of 3D germanium crystals on silicon CMOS for monolithically integrated X‐ray detector

“…X-ray detectors, for which perpendicular electrical transport across the interface to the Si-substrate is of major concern, the current-voltage (I-V) characteristics of single Ge crystal/Si substrate heterojunctions needed to be studied (for preliminary tests see Ref. [13]). In view of the opposite doping type of the Ge crystals and the Si substrate, these heterojunctions are expected to have diode characteristics, whose properties depend on the respective doping levels, interfacial and other defects, and on surface effects.…”

Broadband control of the optical properties of semiconductors through site-controlled self-assembly of microcrystals

“…In this framework, the synergy of top-down and bottom-up techniques with current industrial-grade methods of material fabrication can yield interesting and promising approaches to tailor materials functionalities and performances. It has already been demonstrated [1] that the out-of-equilibrium deposition [2] on deeply patterned Si substrates allows for vertical homo and heteroepitaxy [1,3,4] of various materials including silicon, [4] germanium, [1,[5][6][7]] silicon carbide, [7,8] and III-V semiconductors like gallium nitride [9] and gallium arsenide. [10][11][12] The resulting structures are typically composed of micrometer-sized, deeply etched Si seeds, or "pillars", on top of which high-quality, faceted epitaxial microcrystals develop.…”