Materials Science and Engineering B 108 (2004) 213–218 Boron mediation on the growth of Ge quantum dots on Si (1 0 0) by ultra high vacuum chemical vapor deposition system P.S. Chen ∗ , Z. Pei, Y.H. Peng, S.W. Lee, M.-J.Tsai Electronics Research and Service Organization, Industrial Technology Research Institute, Bldg. 11 195-4, Sec. 4, Chung Hsing Rd. Chutung, HsinChu, Taiwan 310, ROC Received 28 August 2003; accepted 7 November 2003 Abstract Self-assembled Ge quantum dots (QDs) with boron mediation are grown on Si (1 0 0) by an industrial hot wall ultra-high-vacuum chemical vapor deposition (UHV/CVD) system with different growth temperatures and dopant gas flow rates. Diborane (B 2 H 6 ) gas is applied as a surfactant on the Si (1 0 0) prior to the growth of Ge QDs. Small dome and pyramid shaped Ge QDs are observed af- ter boron treatment as compared to the hut shaped Ge cluster without boron pre-treatment at 525 and 550 ◦ C. The Ge QDs have a typical base width and height of about 30 and 6nm, respectively, and the density is about 2.5 × 10 10 cm -2 for the growth tempera- ture of 525 ◦ C. Through weakening the Si–H bond during the epitaxy growth and changing the stress field on the surface of the Si (1 0 0) buffer, boron mediation can modify the growth mode of Ge QDs. When the growth temperature is low (525–550 ◦ C), the for- mer factor is dominate, as the growth temperature is raised (600 ◦ C), the latter parameter may play an important role on the forma- tion of Ge QDs. Optical transition from Ge QDs is demonstrated from photoluminescence (PL) spectra. Furthermore, multifold Ge/Si layers are also carried out to enhance the PL intensity with first Ge layer treated by B 2 H 6 and avoid the generation of threading dislocations. © 2003 Elsevier B.V. All rights reserved. Keywords: Silicon; Germanium; Optical properties; Quantum dot 1. Introduction In recent years, Ge quantum dots (QDs) have been re- ceived much attention because of the unusual electrical and optical properties associated with the quantum con- finement effect [1–3]. One of the fabrication methods for nano-sized Ge QDs is by Stranski–Krastanow (S–K) pro- cess, which forms self-assembled islands during strained layer hetro-epitaxial growth on Si. When Ge QDs grow beyond several monolayers (MLs) and the roughness of the surface increases to a certain extent, the islands are formed [4,5]. Owing to the need of small size Ge QDs islands for better quantum confinement, several methods, including low temperature process [6], carbon adlayer [7,8], and Sb surfactant [9,10] have been reported. The incorporation of boron has also been investigated and shown to have the ability to modify the growth mode of Ge QDs [11,12]. ∗ Corresponding author. Tel.: +886-3-5913189; fax: +886-3-5917690. E-mail address: pschen@itri.org.tw (P.S. Chen). Seal et al. [11] observe that the co-doping of boron can reduce the size and enhance the uniformity of Ge QDs. The boron mediation has also been investigated by the gas source molecular beam epitaxy system. Takamiya et al. [12] reported the two kinds of Ge QDs, presumably due to the strain field induced modification on the surface of Si by boron surfactant with diborane (B 2 H 6 ). However, the effects of growth temperature on the formation of Ge QDs using B 2 H 6 adlayer have not yet been investigated. In this work, the effect of B 2 H 6 treatment prior to Ge QDs growth by an industrial hot wall ultra-high-vacuum chemical vapor deposition (UHV/CVD) system from 525 to 600 ◦ C is reported. To get high quality strained SiGe thin films, hot-wall isothermal UHV/CVD has been used by Meyerson [13]. The drastic modification of the surface morphology and the growth mode of Ge QDs by boron pretreatment are also presented. The possible factor between the growth temper- ature and the amount of B 2 H 6 pre-treatment are discussed. Beside this, to enhance the PL intensity, multi Ge/Si QDs layers were grown on B 2 H 6 pre-treated Si substrates. 0921-5107/$ – see front matter © 2003 Elsevier B.V. All rights reserved. doi:10.1016/j.mseb.2003.11.017