Infrared Optoelectronics

1
Infrared Optoelectronics

• Archie Holmes

2
Overall Research Goal

• My research involves building devices that emit
  or detect light for a wide variety of
  applications
• Devices that emit light are either light-emitting
  diodes (LEDs) or lasers
• Devices that detect light are photodetectors
• Many of these devices need to be developed from
  scratch
• Having the ability to design, make, and test the
  devices is essential

3
MOCVD Growth of III-V Materials
http//britneyspears.ac/physics/fabrication/fabric
ation.htm
4
Outline

• Motivation for Infrared Optoelectronics
• Current Results
• Future Work and Challenges

5
Motivation for Infrared Optoelectronics
6
Application Summary

• Space-based Communications
• Pollution detection
• Industrial process monitoring
• Chemical forensics
• Chemical and biological warfare
• Missile tracking
• Night vision
• Non-invasive medical diagnostics.
• Noninvasive Measurements of Analytes in solution
  concentrations

7
Atmospheric Transmission
SWIR
MIR
LWIR
http//en.wikipedia.org/wiki/Atmospheric_window
8
Vibrational Bands of Molecules

• Nitrous Oxide (N2O) - Absorption at 4.5 mm.
• Important in pollution (automobile emission)
• Ammonia (NH3) - Absorption at 3 mm.
• Signature for acid rain
• Methane (CH4) - Absorption at 3.2 mm.
• An important greenhouse gas
• Carbon Dioxide (CO2) - Absorption at 4.3 mm.
• Important for monitoring the atmosphere
• Also plays role in process control of beverages

9
Blackbody Radiation
10
(No Transcript)
11
Diabetes in America 1990 - 2001
Mokdad et al. Prevalence of obesity, diabetes,
and other obesity-related health risk factors,
2001. JAMA 2003 Jan 1289(1)76-79
12
Absorbance Spectra of Glucose
Olesberg et al., APPLIED SPECTROSCOPY 59 (12)
1480-1484 DEC 2005
13
Current Status Photodiodes
14
Photodiodes on InP-Substrate
295 K
Rogalski, A., Progress in Quant. Elec., 27(2-3),
pp 59 (2003)
Can we build a photodiode on InP with high D at
wavelengths beyond 3 mm?
15
Figures of Merit

• Each photon coming in should be (a) absorbed and
  (b) lead to the collection of an electron
• Called External Quantum Efficiency
• Should be high (approaching 100)
• The generated electrons are being collected as
  current
• Small currents without light are required for
  high sensitivity (called dark current)

16
We have developed InP based photodiodes with
response past 2 µm using type-II GaInAs/GaAsSb
absorption regions

• PIN photodiodes
• A peak detection wavelength of 2.26 µm and
  optical response out to 2.52 µm.
• Dark current densities of 5 mA/cm2 at 293K (-1V
  bias)
• This reduces to 500 µA/cm2 at 250K and 20
  µA/cm2 at 200K.
• Peak external quantum efficiency of 44
• Can be improved with better AR coating
• Estimated internal quantum efficiency gt 90

17

• Avalanche Photodiodes
• Dark current densities of 9 mA/cm2 at 293K (near
  breakdown)
• This reduces to 660 µA/cm2 at 225K.
• Room temperature Gains up to 35 Gains up to 250
  at 225K
• Significant Noise exists in APDs using InP
  multiplication regions

18
Where we are now
19
Future Work and Challenges
20
Challenges for Photodiodes

• Improving Performance of Photodiodes, especially
  at room temperature
• Achieving longer wavelength detection

21
Prospect for MIR Emitters
22
Current Status

• Sb-lasers suffer from heat management and hole
  confinement
• High thermal resistance of Sb-based materials
• Low hole confinement in quantum wells when l gets
  longer
• Can be less than 80 meV as l approaches 4 mm
• Quantum Cascade lasers also suffer from heat
  management
• Voltage is N(transition energy) where N is the
  number of stages
• Power densities greater than 10kW/cm2 expected
  for l less than 4 mm.

23
Initial Modeling for MWIR Emitters

• Wavelengths of interest can be covered
• Currently working with Luke Mawst _at_ Wisconsin on
  developing this technology