Device fabrication

Within the compass of this field we have several goals and a broad range of equipment. The semiconductor device processing and fabrication facilities include a photolithography system with 5mm spatial resolution, a Plasma-Therm Series 790 ICP dry etching system, thermal annealing furnaces, a thermal evaporation system, and a wire bonder. The physical realization of microcavity devices based on GaN, AlGaN, and InGaN epilayers, heterostructures, and multiple quantum wells is achieved by photolithographic patterning and plasma etching technique. Our goal is to proceed from GaN production to actually creating working devices from the raw material such as: light emitting diodes, microlasers, transistors, and so on.

Below: (a) SEM image of a microdisk array fabricated from p-GaN/InGaN/n-GaN quantum wells at KSU. This array is a microdisplay when the disks are individually addressed and forward biased and is a miniaturized detector array when the disks are reversed biased; (b) Optical microscope image of a bonding scheme that allows us to address each microcavity pixel individually (or a III-nitride blue microdisplay); (c) Optical microscope image of the III-nitride blue microdisplay [Fig. (b)] in action, displaying letters "KSU"; (d) Power output vs. input current for three individual micro-LEDs within the microdisplay Fig. (b) and the inset shows the electroluminescence spectrum of these micro-LEDs.

Our laboratory is equipped with a full range of facilities for the nano-fabrication of photonic, optoelectronic, and electronic devices. These include:

• A SEM (LEO-440) based e-beam lithography system for nano-scale device patterning with a line resolution of about 30 nm (60 nm) for conducting (insulating) substrate; 
• One photolithography systems for micro-device patterning (1 mm line resolution);
• One deep UV photolithography systems for sub-micron device patterning (0.25 mm line resolution);
• A Plasma-Therm Series 790 Inductively Coupled Plasma (ICP) etching system for dry etching and pattern transfer;
• Electron beam evaporation and sputtering systems for metal contact deposition
• A flip-chip bonding system (RD Automation) is used for device packaging and for bump-mounting individual or arrays of devices onto sub-mounts or other driving/read-out circuits. This system will be used for imprinting test.
• A sapphire polishing system for thinning the sapphire substrates to allow for wafer dicing;
• Automated wafer scribe/dicing system (Dynatex).
• A PECVD system – Plasma enhance chemical vapor deposition system is used for the deposition of high quality dielectric mirrors, as well as insulating materials on light emitters, waveguides, resonators, transistors, etc.

Other device fabrication and testing accessories:

• A two temperature zone thermal annealing furnace (< 1200 C);
• Two rapid thermal annealing furnace (reaches 1200 C in 5 seconds);
• Probe stations, wire bonders, micromanipulators, optical microscopes;
• Pulse source meters, laser diode drivers;
• Tektronix programmable curve tracer and 45 GHz analog and digital oscilloscopes;
• Ocean Optics spectrometer for quick EL spectra scan;
• Integrated optical sphere for LED characterization;
• Optical transmission/reflectance spectroscopy measurement set.

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