Silicon-Based Integration of Groups III, IV, V Chemical Vapor Depositions in High-Quality Photodiodes

Abstract

Heterogeneous integration of III-V semiconductors with silicon (Si) technology is an interesting approach to utilize the advantages of both high-speed photonic and electronic properties. The work presented in this thesis is initiated by this major goal of merging III-V semiconductor technology with Si technology. The focus was primitively placed on development of a Si-compatible tool for chemical vapor deposition (CVD) of gallium arsenide (GaAs). For this purpose, a Si/SiGe CVD reactor, ASMI Epsilon 2000, was extended with a TriMethylGallium (TMGa) bubbler system and extra tubing to allow the deposition of GaAs as well as the standard Si and SiGe depositions. Of key importance was to apply a very low arsine (AsH3) concentration: 0.7% as compared to the at least ten times higher values normally used in MOCVDs. The correspondingly low concentration of TMGa means that the contamination of the reactor chamber with gallium or arsenic is so low that standard high-quality low-doped Si and SiGe depositions can still be performed in the same CVD reactor chamber. In view of this, the research took a unique direction of creating devices where the merging of depositions of gallium (Ga), arsenic (As) and boron (B), together with Si and Ge, all in one reactor, proved indispensable. For the first time, deposition cycles containing layers of different combinations of these III, IV, V elements could then be performed without vacuum break. This was important not only for the growth of good quality GaAs epitaxy and crystalline Ge-on-Si, but also for the formation of junction diodes in these materials. In particular, the formation of p+n Si diodes of exceptional quality was facilitated by deposition of pure gallium (PureGa) or pure boron (PureB) to create the p+-region. The combination of both PureGa and PureB techniques have been implemented on crystalline Ge-on-Si to form ideal Ge-on-Si p+n junctions with world record low saturation currents. The term PureGaB is introduced for this technology. On the application side, this thesis work has been directed towards the very challenging feat of fabricating Ge avalanche photodiodes (Ge APDs)on Si substrates. The low dark current and clear breakdown curve of these diodes were proven to be suitable for infrared detection in linear and photon counting (Geiger) mode.Microelectronics & Computer EngineeringElectrical Engineering, Mathematics and Computer Scienc