Extremely high quality semiconductor layered structures can be grown by molecular beam epitaxy (MBE) crystal growth technique, in which each molecular sources (Al, Ga, As, etc.) are evaporated in a ultra-high vacuum chamber. Atomically smooth surfaces and interfaces of semiconductor layers with well-controlled thickness and doping concentration are obtained by sequentially depositing sources at proper growth conditions. High-mobility wafers are available at NTT, while moderately-high-mobility wafers (good enough for quantum dots) can be obtained from other suppliers.

Electron beam (EB) lithography is a fundamental tool to define nanometer scale patterns on a surface. After spinning EB resist (typically, PMMA) on a substrate, an electron beam is scanned on the surface to draw arbitrary patterns. Subsequent development removes the exposed resist from the surface (positive process). Fine resist pattern with a resolution of about 20-50 nm can be fabricated. The patterned resist is used to make nanostructures with other processing, such as wet/dry etching, metal/dielectric deposition, etc.

Anisotripic etching of semiconductor is available with reactive ion etching technique. Reactive ion plasma, which contains various kinds of radical ions, is created from clorine gas (Cl2 or BCl3) in an ion source chamber with electron cycrotron resonance (ECR). The plasma is introduced on semiconductor wafer, and etches semiconductor physically or chemically.

Vaccume evaporator is widely used to deposite thin metal layer (Au, Al, Ti, Ni, etc.) on semiconductor. Lift off technique, in which metal layer on patterned resist is removed with the resist by chemical treatment, allows us to fabricate fine metal patterns. Electron beam heating is fevored for lower heat damage to the regist. Metal-semiconductor Shottkey junction is used to tune the carrier density of the underlying conductive layer.

Dilution refregerator allows us to measure electrical properties at below 10 or 100 mK. When He3 and He4 mixture is cooled down below 1.7 K, it decomposes into He3 dense phase and He3 dilute phase. When He3 atom penetrates from the dense phase to the dilute phase in a mixing chamber, the entalphy change works as cooling process. He3 gas is collected from the dilute phase in a still chamber with heating (about 0.8 K), and is condensed into 1K pot, returing into the dense phase in the mixing chamber. Since cooling process works continuously, one can measure samples at low-temperature continuously (more than a few months).

Low-noise electronics is essental for measureing quantum effects in a small current of high-impedance devices, such as quantum dots. All electrical wires in a dilution refregeraror has to be installed with low-temperature filtering, such as copper powder filters, thin coaxial cables together with conventional RC filters. In addition, battery driven front-end electronics are recommended to reduce 50 Hz problems.

High frequency measurement is recently understood as fundamental technique to investigate dynamical characteristics of low-dimensional electron systems. State-of-the-art electronics provide microwave signal up to 50 GHz or higher with phase-locked loop. Pulsed microwave is also available with internal/external fast switches. High-speed voltage pulse with rise/fall time of 30-40 ps are also available owing to opto-electronic applications. Moreover, low-noise high-frequency devices are important for detecting small amplitude signal from quantum devices. Some microwave amplifier works well (noise figure < 0.4dB) at cryogenic temperature.