PTCOE's Capabilities at Georgia Tech


PTCOE has advanced thin-film deposition facilities which include CVD, electron beam and sputtering systems, MBE/VPD and a large-area Ion Assisted Deposition (IAD) systems. PTCOE's research faculty have extensive experience in the deposition of inorganic materials by metalorganic and molecular beam epitaxy as well as e-beam and thermal evaporation processes. These systems have been used to deposit all types of materials such as SrS:Cu,Ag, SrS:Ce, ZnS:Mn, CaS:Cu, SrGa2S4:Ce, LaO2S:Tb, GdO2S:Tb, Si, InAlGaAsP, HgZnCdTe for displays and optoelectronic device applications. These deposition capabilities are complemented by insitu control and characterization techniques such as reflectance, reflection high energy electron diffraction, residual gas analysis, quadrupole mass spectrometry and auger electron spectrometry. Also, growth enhancement capabilities are available including photoassisted deposition and ECR plasma sources.Extensive expertise in the optical and electrical doping of these materials has been developed. PTCOE's deposition systems have the capability to handle low and high vapor pressure materials using conventional solid source evaporation, valved crackers and gas sources (organometallics and high pressure gases). In addition, several unique delivery systems have been developed, which allow precise control over very high vapor pressure materials and gas sources with control of flows over 6 orders of magnitude.

PTCOE's large-area IAD system allows the simultaneous co-evaporation of four materials (thermal and electron beam) and the low temperature deposition of high quality oxide materials.

Summary of IAD Capabilities

  • Large-area flexible manufacturing/research tool
  • Four thermal evaporation sources
  • One 4-pocket e-beam evaporation source
  • Can operate four sources simultaneously
  • Individually shuttered sources
  • Can control evaporation rates before shutters open
  • Substrate temperatures to 600oC
  • Uniform low voltage (40-150V), high current density plasma source
  • One meter diameter deposition area

Molecular Beam Epitaxy (MBE) System used for deposition of novel EL phosphors

Large-area Ion-Assisted Deposition (IAD) System for Low-temperature Electron Beam and Thermal Evaporation

Inside View of the IAD System Pictured Above 



  • AMI automatic vision alignment screen printer (above), 144mm, 200mm substrates
  • Windows95 automated system
  • Image capture package
  • Double squeegee head 
  • 12, 15, 24 in (square) tooling 
  • up to 18"x20" printable area
  • Servo-motorized in x,y,z motion 
  • Repeatable accuracy - 0.0004 in.
  • Traditional Slurry-Spin coater  (above left)
  • Tri-color masks Automated
  • UV Exposure cabinet (above right)
  • Capable of coating up to 5 inch plates
  • Screen Aluminization Capability (below)
  • 3 Hood stations, 2-oxide, 1-sulfide
  • 2-1500, 1-1700, 2-1200 °C furnaces:
    • programable up to 8 ramp/time steps
    • vacuum to 10-3 Torr
    •  flowing or stationary atmospheres
  • Vibratory Grinding Mill- Sweco M18-5
  • Buchi 190 Mini Spray Dryer
  • Drying ovens, Vacuum Oven, Freezing Dryer
  • Scanning Electron Microscope (SEM), Transmission Electron Microscope (TEM), Differential Thermal Analysis/ Thermal Gravity (DTA/TG)
  • Leeds+Northrup Particle Size Analyzer; 0.1-700 m


To assess the quality of material layers, a variety of material and surface characterization techniques are available. The capabilities include Photoluminescence (PL), PL Excitation Spectroscopy (PLE), Charge Deep Level Transient Spectroscopy (QDLTS), Secondary Ion Mass Spectrometry (SIMS), Scanning Electron Microscopy (SEM), and X-ray diffractometry. Other analytical instrumentation a Transmission Electron Microscope (TEM), an Atomic Force Microscope (AFM), and X-ray crystallography equipment.

PTCOE's Automatic System of Materials Electrical Characterization (ASMEC) was specifically designed for electrical & photoelectric characterization of dielectric and wide gap semiconductors such as CaF2/ZnS/SrS. It uses powerful techniques such as Q-DLTS and Photo-stimulated Internal Field Transient Spectroscopy (PIFTS) to provide information on bulk/interface trap activation energies and capture cross sections, as well as trap concentration.

Charge Deep Level Transient Spectroscopy

  • Q-DLTS - temperature scan and isothermal rate window scan with electrical or optical excitation
  • I-V - Current-voltage ( 2 and 4 probe methods)
  • Ie-V(Vg) - Emission current measurements
  • C-V - Capacitance-voltage (pulse and line scanned)
  • IFTS - Internal Fields Transient Spectroscopic 
Main System Specifications
  • current and photocurrent sensitivity, 1 pA
  • charge sensitivity, 5 x 10-16 C
  • deep level concentration sensitivity Nt / N~5x10-7
  • range of bias voltage, +/- 10 V
  • range of time (rate) window duration, 2 x10-6-200 s
  • temperature range, 80 - 200 K

The photoluminescence spectroscopy system can be used to achieve above bandgap and direct excitationby deep- and/or mid UV lasers, a Xenon arc lamp and a Deuterium arc lamp. The resulting luminescence is analyzed with the detection system and provides information on the crystalline quality and impurities. In addition, a tunable light source allows PL excitation spectroscopy, which can be used to investigate the excitation mechanisms and the electronic structures of the luminescent centers in semiconductors. The dynamical properties of the luminescence such as excitation energy transfer can also be investigated by using pulsed lasers.

Optical Spectroscopy Laboratory


  • Deuterium lamp (150W): 115 - 400nm, Xe lamp (450W): 200 - 1200nm
  • Spectra-Physics Ar ion laser: 275, 488 and 514nm 
  • Spectra-Physics Ti-Sapphire laser: 700nm - 1?m
  • Liconix HeCd laser: 325 and 442nm, Spectra-Physics HeNe laser: 632.8nm
  • Lambda-Physik Excimer laser: 157, 193, 248 and 351nm, 25 - 30ns pulse
  • Spectra-physics Nd:YAG laser: 1064, 532 and 355nm, 10ns pulse
  • Spectra-Physics MOPO laser: 220 - 1800nm, 8ns pulse
  • Laser-Photonics N2/Dye laser: 337nm, 473 - 547nm, 600ps pulse
  • Acton VM502 scanning VUV monochromator
  • Spex 1000M, 1681, 270M monochromators
  • VUV photomultiplier tube (PMT), Liquid N2 cooled Ge detector
  • CCD array, Thermoelectrically cooled GaAs PMT, Si, InAs and InSb diode detector
  • EG&G 5208 lock-in amplifier, EG&G 162 boxcar integrator
  • Tektronix 602 fast digitizing oscilloscope
  • Temperature range
    • Helium displex system - 10K ~ 350K
    • Liquid helium dewar - 1.6K ~ 350K


To obtain accurate cathodoluminescent (CL) intrinsic efficiency measurements, both the reflected and transmitted light components are measured by employing a two-photometer system. This procedure provides an accurate correction for the transmitted emission losses of different phosphors. Both photometers sample the same excited area within the e-beam spot. A Faraday cup is also used in the sample holder to determine the e-beam current before the measurement. A fast response EFG-7F e-gun with a range from 0-5 kV is used for these measurements. The vacuum system has two viewports available for the two photometers. Its transport arm is centered on the beam axis, and a guide rail (which holds the rotation angle constant as the samples are translated) is used. The transport arm can also be attached to a motorized translation stage. This stage can be computer-controlled to translate the samples across the e-beam automatically, and take the measurements. The photometer also enables the sample chromaticity to be obtained in the same measurement. In addition, the PMT/monochromator system can be quickly put in place to measure the CL decay time of the different phosphors using the E-gun in the pulsed mode. Decay times down to 50 ns can be measured.

The saturation, transient analysis, and aging studies are conducted in a vacuum chamber equipped with Fison LEG 32 (0-5 kV) and LEG 320 (1-30 kV) E-guns. The LEG 32 has been well characterized for beam size and current density. A Faraday cup at the bottom of the chamber measures and monitors any changes in beam current. The LEG 320 gun is used for high energy intrinsic efficiency measurements, and in addition, provides a means for extracting diffusion length and surface recombination parameters. 

Brightness Saturation Characterization System

Cathodoluminescence Luminous Efficiency System

Phosphor Screen Test Chamber

Specifications of E-guns used in the Cathodoluminescence Studies

Low Current Electron Guns

-  Electron energy: 50 eV to 20 keV
-  Target current density: <1 mA/cm2 to 300 mA/cm2
-  Target spot size: 3 mm uniform or > 1 mm Gaussian
-  Pulse width: 10 ns, DC, raster
-  Current monitor: retractable Faraday cup

High Current Electron Guns

-  Electron energy: 100 eV to 30 keV
-  Target current density: < 1 mA/cm2 to > 200 mA/cm2
-  Target spot size: > 50 mm Gaussian or  1 mm Gaussian
-  Pulse width: 300 ns, DC, raster
-  Current monitor: retractable Faraday cup



PTCOE has access to Georgia Tech's Microelectronics Research Center (MiRC), which is housed in a new (1989) 100,000 sq.ft. building plus a 20,000 sq. ft. annex. MiRC includes six electronic and optoelectronic materials labs, eight labs for microelectronic design and testing, and eight labs for electronic device design and testing. A 7,000 sq.ft. cleanroom provides complete microfabrication facilities. Specialized materials growth and vacuum deposition systems are also available for fabrication of thin film semiconductor devices in a variety of material systems including III-V and II-VI semiconductors. The photolithography area is a class 1000 room with specialized mask aligner exposure stations suitable for photolithography into the submicron range. Other specialized equipments include surface preparation systems and scanning electron microscopes.

Partial List of Cleanroom Equipment available at Georgia Tech's MiRC:

  • CEE 100CB Spin Coater 
  • CVC DC Sputterer 
  • CVC Electron Beam Evaporator 
  • CVC Filament Evaporator 
  • CVC RF Sputterer 
  • Edwards Auto 306 Sputterer 
  • LFE Barrel Etcher 
  • Lindberg Furnaces 
  • Plas-Mos Ellipsometer 
  • Plasma-Therm PECVD 
  • Plasma-Therm RIE #1 
  • Plasma-Therm RIE #2 
  • Plasma-Therm ICP 
In addition to the MiRC facilities, PTCOE also has available a dedicated sputtering machine for the deposition of dielectric and transparent conducting materials. A Perkin Elmer 2400 diode sputtering system has been modified by addition of an RF, A340 Magnetron Sputtering Source. The A340 Magnetron Sputtering Source includes a modular magnet array, clamping ring for 4" diameter, ¼" thick, non-magnetic targets. 

RF Sputtering System

E-beam Evaporation System 



PTCOE has extensive optical and electrical techniques for the analysis and characterization of emissive and non-emissive displays as well as various optoelectronic devices such as photodiodes and Light Emitting Diodes (LEDs). Various computer-automated experiments are available to measure and analyze the macroscopic & microscopic properties of thin-film heterostructure devices. A practical probe test station has been designed and constructed for electrical characterization measurements of optoelectronic and display devices. Both high-voltage (150-250 V) and low-voltage (20-30 V) EL devices can be investigated by applying unipolar and bipolar rectangular pulse with different pulse widths. Two photometers (PR 650 & 880) are available to measure device intensity (brightness) and CIE coordinates. A brief description of some of these capabilities and the information they provide about the device under test is presented in the table below.
Information Provided
EL Spectroscopy
CIE Chromaticity
B-V, h-V, I-V
Q-V, C-V
V-t, I-t
Output brightness, spectrum and chromaticity as a function of bias and pulse width, current/charge-voltage properties Threshold voltage, display/LED luminance, CIE coordinates, luminous efficiency, angular dependence.
Device capacitance, charge differential and spectroscopy as a function of bias and temperature Carrier concentration, capture cross section, activation energy, depletion width, defect/trap densities.
Photodiode Transient Response Response to short (~50 ps) and high power laser pulses Decay time/bandwidth characteristics of devices 
All of the above measurements can be performed at temperatures ranging from 90 K to 400 K using an R2400-20 MMR Micro Probe Station and a K-20A Temperature Controller.

Display & Device Characterization System

Shielded Optoelectronic Device Testing Laboratory



PTCOE has a suite of advanced semiconductor device simulation tools (Silvaco's TCAD). These software packages contain both microscopic as well as macroscopic device simulators, which provide a coupled, hierarchical approach to semiconductor device modeling. Silvaco's device simulation software uses powerful numerical techniques to solve for the various properties of homojunction/heterojunction devices under different operating conditions. A built-in optimizer allows for quick and accurate tuning of simulation parameters. The following is an overview of the general capabilities of Silvaco's ATLAS which includes the following tools and extensions:
  • ATHENA: Two-dimensional process simulation framework for modeling semiconductor fabrication processes such as impurity diffusion, oxidation, topography, and lithography.
  • BLAZE: Simulates devices fabricated using arbitrary semiconductors (including II-VI, III-V, and IV-IV materials), and heterojunctions.
  • GIGA: Adds the ability to perform nonisothermal calculations that include the effects of lattice heating and heat sinks.
  • MIXEDMODE: Offers circuit simulation capabilities that employ numerical physically-based devices as well as compact analytical models.
  • DEVICE3D: Provides capabilities for three-dimensional device simulation.
  • THERMAL3D: Provides capabilities for three-dimensional thermal analysis.
Furthermore, PTCOE uses sophisticated Design of Experiment (DOE) and Statistical Process Control (SPC) software to design and analyze experimental results and to enable technology transfer to manufacturing. DOE helps maximize the information gleaned from a minimal number of runs and allows the use of "randomization" to remove time-varying effects from the results, and "blocking" to remove known or suspected biases.

PTCOE also employs Monte Carlo simulations in the analysis of CL phosphor properties, which incorporates the known physics of elastic and inelastic scattering processes for electrons incident on amorphous materials. The simulation reliably predicts range values for the primary electrons incident on the host and the electron range can be quickly calculated for many phosphors.

Two-dimensional Electrical/Optical Simulation of an Optoelectronic Device

Statistical Analysis of EL Device Performance using Response Surface Methodology (RSM)