Fan Ren
ExxonMobil Gator Chemical Engineering Alumni Professorship
Distinguished Professor
 
Semiconductor Materials and Devices

317 Chemical Engineering Building
 
Phone : (352) 392-4727
e-mail : ren@che.ufl.edu
 
Research Interests
 
ZnO Nanowires for Sensing And Device Applications
 
ZnO is a piezoelectric, transparent wide bandgap semiconductor used in surface acoustic wave devices. The bandgap can be increased by Mg doping. ZnO has been effectively used as a gas sensor material based on the near-surface modification of charge distribution with certain surface-absorbed species. In addition, it is attractive for biosensors given that Zn and Mg are essential elements for neurotransmitter production and enzyme functioning. ZnO is readily synthesized in the form of nanowires, which are attractive for UV sensing as well as gas and chemical sensing, and the ability to control their nucleation sites makes them candidates for micro-lasers or memory arrays. We have fabricated many types of ZnO nanowire devices, including MOSFETs, diodes, UV sensors and pH sensors. ZnO has been effectively used as a gas sensor material based on the nearsurface modification of charge distribution with surface-absorbed species.
 
AlGaN/GaN High Electron Mobility Transistors(HEMTs) Based Sensors
 
Ungated AlGaN/ GaN High Electron Mobility Transistors also exhibit large changes in current upon exposing the gate region to polar liquids. The polar nature of the electrolyte introduced led to a change of surface charges, producing a change in surface potential at the semiconductor /liquid interface. By functinalizing the surface of the AlGaN/GaN HEMTsurface, HEMT can be used for a variety of chemicals.
 
Oxide Based Optical and Electronic Devices
 
There is also a strong interest in developing oxide based thin film transistors due to higher transparency and better carrier mobility as compared to amorphous silicon. Amorphous or nanocrystalline n-type oxide semiconductors such as zinc oxide, zinc tin oxide, indium gallium oxide and indium gallium zinc tin oxide have shown surprisingly high carrier mobilities (~10 cm2 V-1 s-1) even for amorphous films deposited at room temperature. These transparent conducting oxides may also be used as electrodes in solar cells and flat-panel display devices.
 
InGaAs Based MSM Detector
 
Laser detection and ranging (LADAR) is the light-based analog of the common radar. LADAR is attractive for military applications, such as reconnaissance, weapons fusing, mapping, and facial recognition. The Army Research Laboratory (ARL) Sensors and Electron Devices Directorate has been developing a FM/cw incoherent laser detection and ranging (LADAR) system. This LADAR system uses an interdigitated metal-semiconductor-metal (MSM) photodetector in optoelectronic mixer (OEM) mode developed through a collaboration between ARL and the University of Florida.
 
AlGaN/GaN High Electron Mobility Transistors(HEMTs) Passivation
 
AlGaN/GaN high electron mobility transistors (HEMTs) show great promise for applications, such as high frequency wireless base stations and broad-band links, commercial and military radar and satellite communications. One problem commonly observed in these devices is the so-called “current collapse” in which the application of a high drain-source voltage leads to a decrease of the drain current and increase in the knee voltage. This phenomenon can also be observed by a current dispersion between dc and pulsed test conditions or a degraded rf output power. Proper passivation can minimize this degradaton.