Wide Band Gap Semiconductors Group at YSU

Why Wide Band Gap Semiconductors?

A Wide Band Gap (WBG) semiconductor in general terms can be defined as a semiconductor with an energy band gap (E_G) above 2 eV. Included in this group are the group III-nitrides, silicon carbide (SiC), zinc selenide (ZnSe) etc. The focus of our group is on the group III-nitrides, silicon carbide and zinc oxide.
Present-day commercial satellites, modern jet aircrafts, automobile engines, sub-sea well logging systems, etc require thermal radiators to dissipate heat generated by the functional electronics. High temperature electronic systems for such functions require electronic devices that retain their functions and reliabilities up to the desired operation temperature as well as an interconnection technology on a substrate to form an electronic circuit with long-term operation capability. Currently, these electronics are based on traditional semiconductors such as silicon or gallium arsenide, which would fail if they were not properly cooled. The cooling system introduces serious drawbacks including addition of a substantial amount of weight, which lowers the efficiency and reliability of the devices. As a result, wide band gap semiconductors such as group III-nitrides, silicon carbide and zinc oxide have recently attracted a great deal of attention. These semiconductors offer the possibility of realizing exciting new electronic devices for high power, high temperature and high frequency operations enabling substantial savings, increased performance and reliability. The III-nitrides and zinc oxide in particular can be used in a variety of opto-electronic devices operating in shorter wavelength regions than could be possible with silicon or gallium arsenide.

Group III-nitrides:
The group III-nitrides comprise gallium nitride (GaN, E_G = 3.4 eV), aluminum nitride (AlN, E_G = 6.2 eV) indium nitride (AlN, E_G = 0.8 eV) an their alloys.

Silicon carbide:
 Silicon carbide (SiC) exists as a family of crystals known as polytypes. The difference among the polytypes is in the arrangement of layers of silicon (Si) and carbon (C) and over 200 polytypes of SiC are known to exist. Only one cubic (zincblende) polytype 3C, with E_G = 2.39 eV exists and the rest are hexagonal (wurtzite). Of the wurtzite polytype, the important ones are 4H  (with E_G = 3.27 eV) and 6H (with E_G = 3.02 eV). Silicon carbide possesses extremely high thermal, chemical, and mechanical stability. Its extreme mechanical stability is the reason for its use as a coating for drill bits and saw blades. Because of its large band gap energy, the thermal generation of electron-hole pairs  in SiC is many orders of magintude lower at any given temperature compared to silicon. This makes it possible to build "dynamic" memories (DRAMs) in SiC that only need to be refreshed about once every 100 years at room temperature! This also makes it possible to operate SiC devices at temperatures as high as 650 °C without degradation in electrical performance. The breakdown electric field in SiC is about 8 times higher than in silicon, making SiC very attractive for fabricating high-voltage power switching transistors.

Collaboration with our group:

Ashley Snipes (High School Intern, Summer 2011)

Andrew Smith at the MRS Meeting in Boston, MA

Michael McMaster (BS student, Physics)

Nagaraju Velpukonda (MS student, Electrical Engineering)

Devin at the new Karl-Suss Mask Aligner

Michael Nycz at the PL System

Luch at QUEST

Rani Kummari performing data analysis

Dr. Oder with High School students

Condensed Matter Physics Class 5830

Mark Barlow preparing a sample

Edward Sutphin at the mask aligner

Aaron Schott doing RTP annealing

Sara Schaefer at the mask aligner

Rani  Kummari preparing samples

Photonic, Optical, Electronic Materials (POEM) Group

Mark Del Fraino at work

Pam Martin Using I-V Characterization System

Matt Crummel installing the Sputtering System