MBE growth of tensile-strained Ge quantum wells and quantum dots

doi:10.1007/s12200-012-0193-x

Front Optoelec

2012, Vol. 5

Issue (1) : 112-116 https://doi.org/10.1007/s12200-012-0193-x

RESEARCH ARTICLE

MBE growth of tensile-strained Ge quantum wells and quantum dots

Yijie HUO¹(

), Hai LIN², Robert CHEN¹, Yiwen RONG¹, Theodore I. KAMINS¹, James S. HARRIS¹

1. Department of Electrical Engineering, Stanford University, Stanford, California 94305, USA; 2. Department of Materials Science and Engineering, Stanford University, Stanford, California 94305, USA

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Abstract

Germanium (Ge) has gained much interest due to the potential of becoming a direct band gap material and an efficient light source for the future complementary metal-oxide-semiconductor (CMOS) compatible photonic integrated circuits. In this paper, highly biaxial tensile strained Ge quantum wells (QWs) and quantum dots (QDs) grown by molecular beam epitaxy are presented. Through relaxed step-graded InGaAs buffer layers with a larger lattice constant, up to 2.3% tensile-strained Ge QWs as well as up to 2.46% tensile-strained Ge QDs are obtained. Characterizations show the good material quality as well as low threading dislocation density. A strong increase of photoluminescence (PL) with highly tensile strained Ge layers at low temperature suggests the existence of a direct band gap semiconductor.

Keywords Si photonics germanium (Ge) tensile strained photoluminescence (PL)

Corresponding Author(s): HUO Yijie,Email:yijiehuo@gmail.com

Issue Date: 05 March 2012

Cite this article:

Yijie HUO,Hai LIN,Robert CHEN, et al. MBE growth of tensile-strained Ge quantum wells and quantum dots[J]. Front Optoelec, 2012, 5(1): 112-116.

URL:

https://academic.hep.com.cn/foe/EN/10.1007/s12200-012-0193-x
https://academic.hep.com.cn/foe/EN/Y2012/V5/I1/112

Fig.1 Cross-section TEM image for strained Ge samples. (a) Schematic of the sample structure; (b) cross-section TEM image of InGaAs buffer layers and the Ge QW; the dash circles are the two selective area diffraction regions in Fig. 2; (c) cross-section TEM image of Ge QW; and (d) high resolution TEM image of Ge QW region

Fig.2 (a) Selected area diffraction; (b,c) zoom-in images from InGaAs and InGaAs buffer layers; (d) diffraction pattern and (e, f) zoom-in images from InGaAs and Ge layers shown in Fig. 1(b)

Tab.1 Biaxial tensile strain inside Ge with different InGaAs buffer layers as measured by Raman and XRD

Fig.3 Low temperature (5 K) PL of different tensile strained Ge layers

Fig.4 1 μm × 1 μm AFM image of Ge QDs on InGaAs buffer layer

Fig.5 SEM image of Ge QD on InGaAs buffer layer

Fig.6 Raman for Ge QD with and without InGaAs capping layer

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