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Research facilities

Overview
A large variety of techniques is used on a regular base for the characterization of semiconductor materials and devices. Our facilities are to a large extent shared within the Center for Advanced Materials' Electronic Materials program (CAM EMAT, Director Prof. Eugene E. Haller) of the Lawrence Berkeley National Laboratory (LBNL) Materials Science Division (MSD), and the Integrated Materials Laboratory (IML) of the University of California, Berkeley (Director Eicke R. Weber). Some facilities are made available through LBNL's Materials Science Division (MSD, Director D. S. Chemla). In addition we make plentiful use of the services provided by LBNL's User Facilities , noteworthy the National Center for Electron Microscopy (NCEM), the Advanced Light Source (ALS), and the 88-Inch Cyclotron . We commonly perform processing of simple devices in the Microfabrication Laboratory (Operations Manager ~Katalin Voros) of the University. Currently, we grow semiconductor materials using molecular beam epitaxy at the Integrated Materials Laboratory (Arsenides) and at the Center for Advanced Materials' (Nitrides).

Below is a list of our most-frequently used tools with some specifications.

Structural Characterization

X-Ray Diffraction (XRD, IML)

  • Siemens D5000 x-ray diffractometer
  • four-circle goniometer
  • Cu tube operated at 40 kV and 30 mA
  • double-crystal four-bounce Ge monochromator 0.154056 nm

Transmission Electron Microscopy (TEM, NCEM)

  • Plan-view and cross section transmission
  • Topcon 002B and JEOL 200CX microscopes, 200kV
  • Philips CM 300 operated at 300kV

Atomic Force Microscopy (AFM, LBNL's MSD)

  • Park Scientific atomic force microscope
  • operated in air
  • scan rate of 1 Hz
  • tip force of 1 nN

Rutherford Backscattering (RBS, CAM EMAT)

  • collimated beam of ionized He particles
  • 1.95 MeV kinetic energy
  • Li-drifted Ge detector

X-Ray Photoelectron Spectroscopy (XPS, IML)

  • Perkin Elmer PHI 5400
  • Mg Ka
  • energy resolution of ~1 eV

Scanning X-Ray Photoemission Microscope (MAXIMUM, ALS)

  • photoemission microscope at the undulator Beamline 12.0.1.1
  • monochromatic 130 eV photon energy
  • spot size of 0.75 mm.

Scanning tunneling microscopes (STM)

  • Room temperature STM
  • Low temperature STM (12 K) with light collection stage for luminescence measurements
  • both STM are beetle type, UHV capable, homebuild with special design for sample cleavage and cross sectional measurements

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Optical Characterization

Photo/Electroluminescence visible/UV (PL/EL, CAM EMAT)

  • PL: HeCd laser (325 nm) 10 mW excitation
  • EL: constant-current excitation of LEDs
  • 0.85 m Spex 1404 double monochromator, 1800 gr/mm, blazed at 400 nm
  • GaAs photomultiplier detection (lock-in technique)
  • closed-cycle He refrigerator (10 K) and/or liquid N2 cryostat (77 K)

Photoluminescence infrared/visible (PL, CAM EMAT)

  • Ar-ion laser (477 nm ... 515 nm) 20 mW excitation
  • 0.22 m Spex 1680 double monochromator, 600 gr/mm, blazed at 1500 nm
  • Ge photodiode detection (lock-in technique)
  • closed-cycle He refrigerator (10 K) and/or liquid N2 cryostat (77 K)

Time-Resolved Photoluminescence (TR-PL, CAM EMAT)

  • Coherent Mira 900 Ti:sapphire mode-locked excitation
    • 5 W Coherent Verdi pump laser (532 nm)
    • tunable between 700 nm and 1000 nm
    • 200 fs pulse length
    • 76 MHz (13 ns) repetition rate
    • 500 mW peak average power (at 800 nm)
  • U-Oplaz doubler and tripler for excitation pulses with wavelength as short as 700 nm / 3 = 233 nm
  • Hamamatsu C5680 streak camera with synchroscan and slow-scan inserts, 2 ps maximum time resolution

Chromex single-grating spectrometer with three gratings: (ruling-blaze) 150 gr/mm-500 nm, 1200 gr/mm-400 nm, 1200 gr/mm-800 nm



Example of a TR-PL spectrum obtained with our set-up on a GaN quantum well embedded in AlGaN barriers. The time and wavelength scale is from top to bottom and from left to right, respectively. SHG indicates stray light from the second-harmonic generation, which can be used as temporal reference mark. The actual excitation was with the third harmonic from the tripler at 270 nm.


Photoreflectance (PR, CAM EMAT)

  • Deuterium and Xenon broadband light sources
  • HeCd laser (325 nm and 442 nm) 50 mW modulation
  • Spex double monochromator
  • Si and/or Ge-diode detection (lock-in technique)

Cathodoluminescence (CL, Weber group)

  • Jeol JSM-35CF scanning electron microscope (SEM)
  • Oxford liquid N2 cryo-stage
  • single-grating imaging spectrograph
  • liquid N2-cooled Si-CCD detection



Example of a CL study we carried out on an AlGaN/GaN heterostructure exploiting the depth-resolution achievable by variation of the electron energy
.



Optical microscopy (CAM EMAT)

  • Zeiss Axioskop
  • 2.5x, 5x, 20x, and 50x objective lenses
  • 10x eyepiece and 12.5x photograph port
  • bright field, dark field, and interference contrast

Ellipsometry (Rubin's group)

 

X-ray Fluorescence Microprobe

  • Maps transition metal impurity distributions in silicon with micron scale resolution
  • Sensitivity: can detect 1015 of Cu and 1013 of Fe
    in silicon; most transition metals detectable at least to 1015
  • When combined with XBIC, can simultaneously map recombinative and chemical properties of impurities in silicon

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Electrical Characterization

Hall Effect (CAM EMAT)

  • 0.28 T magnet
  • switching matrix for full four-terminal characterization
  • liquid-He cryostat

Deep-Level Transient Spectroscopy (DLTS, Weber group)

  • fast capacitance meter and current-voltage converter: capacitance and current DLTS
  • transient recorder set-up, 12 bit ADC, 15000 points
  • rectangular lock-in correlation function
  • pulse width variation, 20 ns minimum width
  • liquid-He cryostat

Low-Frequency Noise Characterization (Weber group)

Device characterization (Weber group)

  • dark-box needle prober set-up (room temperature)
  • HP4140B picoamp meter
  • HP4277A LCZ meter

MMR Low-Temperature MicroProbe set-up (77 to 400 K)

  • HP4140B picoamp meter
  • HP4280A 1 MHz CV meter
  • HP4145A semiconductor parameter analyzer

X-ray Beam Induced Current (XBIC, ALS)

  • Uses synchrotron radiation to map the recombinative properties of impurities in Si to depths of hundreds of microns with a resolution of about 10 microns
  • When combined with XRF and micro-XRF, can simultaneously map recombinative and chemical properties of impurities in silicon

 

Electron Beam Induced Current (EBIC, Weber group)

  • Jeol JSM-35CF scanning electron microscope (SEM)
  • Oxford liquid N2 cryo-stage

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Magnetic Resonance

Electron Paramagnetic Resonance (EPR, CAM EMAT)

  • Bruker ER200
  • 1.2 T magnet
  • 9.5GHz (X-band) TE102 cavity
  • Oxford cryostats 4.2 K and 1.8 K

Magnetic Circular Dichroism of Absorption and Optical Detection of Magnetic Resonance (ODMR, Weber group)

  • Oxford magnet cryostat 1.5 K, 5 T
  • L-N2 cooled Ge-dector, spectrometer and Stanford Rearch HR 350 Lockin-amplifier - capability for IR absorption, MCD and ODMR
  • 42 kHZ quartz stress modulator (for MCD)
  • 20 GHz (K-band) microwave cavity for ODMR


MCDA spectra of positively charged As-antisite defects in non- stoichiometric GaAs. Doping with Be increases the antisite concentration proportionally as can be seen from the increase of the line at 0.94 eV


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External Stimuli

Hydrostatic pressure cell (Weber group)

  • Unipress LOC 10 liquid optical cell
  • 1.2 GPa maximum pressure
  • 1 to 400 K temperature range
  • 12 electrical connectors
  • sapphire window

Biaxial strain cell (Weber group, self-made)




Laser lift-off

Particle irradiation

  • 12 MeV to 55 MeV protons (Berkeley Cyclotron)
  • 1015 protons/cm2 per day

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Please e-mail Peng updates

Last revised: 04/01/02

 

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