Nanostructuring of III-V materials
The technological development creates an ever increasing demand to the functionalities of (opto)electronic components closely related with their miniaturization. At the present time a challenging goal is the controllable and reproducible preparation of structures in sub-10 nm region, i.e. with dimensions up to two orders bigger than those of atoms, applying different nanostructuring techniques, like high resolution electron beam lithography, wet chemical etching and plasma reactive ion etching.
Our current research activities in the field of nanostructuring are directed to patterning of III-V semiconductor materials and Si in order to achieve templates for the tailored growth of self-assembled quantum dots. For lateral structuring, a high resolution electron beam with a lateral laser stage resolution of 2 nm and a beam diameter of 1.6 nm at 20 kV is applied (Fig. 1). For vertical structuring, we use wet chemical etching or dry inductively coupled plasma reactive ion etching (ICP-RIE) (Fig. 2). The latter equipment enables the etching of high-aspect ratio structures in III-V materials, Si and insulators applying a variety of reaction gases (Cl2, BCl3, N2, H2, SF6, CH4, Ar, O2 and CHF3). In the cases when the resist mask is not sufficient, additional thin films of metals (Ti, Pt, Au, Al, Cr, Ni, Zn and Ge) prepared by evaporation and sputtering, or layers of SiO2 and Si3N4, obtained by plasma enhanced chemical vapor deposition (PECVD) are used as mask materials.
Our actual results include the preparation of nanostructured templates for overgrowth with quantum dots by molecular beam epitaxy (MBE) (Figs. 3 and 4). Because the dots grow preferentially in the etched holes, it is possible to control the QD lateral position, extremely important for the alignment of an optical resonator, e. g. a PC-cavity (Photonic Crystal) to a single quantum dot. Such a system will work as a single photon source (see project Q-Photon).
Another application is the structuring of semiconductor lasers, e. g. for the preparation of the optical mirrors (Fig. 5) (see projects www brighter.eu and DeLight).
Our current research activities in the field of nanostructuring are directed to patterning of III-V semiconductor materials and Si in order to achieve templates for the tailored growth of self-assembled quantum dots. For lateral structuring, a high resolution electron beam with a lateral laser stage resolution of 2 nm and a beam diameter of 1.6 nm at 20 kV is applied (Fig. 1). For vertical structuring, we use wet chemical etching or dry inductively coupled plasma reactive ion etching (ICP-RIE) (Fig. 2). The latter equipment enables the etching of high-aspect ratio structures in III-V materials, Si and insulators applying a variety of reaction gases (Cl2, BCl3, N2, H2, SF6, CH4, Ar, O2 and CHF3). In the cases when the resist mask is not sufficient, additional thin films of metals (Ti, Pt, Au, Al, Cr, Ni, Zn and Ge) prepared by evaporation and sputtering, or layers of SiO2 and Si3N4, obtained by plasma enhanced chemical vapor deposition (PECVD) are used as mask materials.
Our actual results include the preparation of nanostructured templates for overgrowth with quantum dots by molecular beam epitaxy (MBE) (Figs. 3 and 4). Because the dots grow preferentially in the etched holes, it is possible to control the QD lateral position, extremely important for the alignment of an optical resonator, e. g. a PC-cavity (Photonic Crystal) to a single quantum dot. Such a system will work as a single photon source (see project Q-Photon).
Another application is the structuring of semiconductor lasers, e. g. for the preparation of the optical mirrors (Fig. 5) (see projects www brighter.eu and DeLight).
Fig.1: High resolution electron beam lithography
Fig.2: Inductively coupled plasma reactive ion etching set-up
Fig.3: Hole pattern in GaAs with 60 nm distance comparable with the density of self-assembled growth
Fig.4: Low density hole pattern in GaAs for single photon devices. The distance between the holes is 2 µm.
Fig.5: GaAs grid with a period of 400nm and a depth of 180 nm produced by Cl2/Ar dry etching in ICP-RIE
