Electrically Injected GeSn Lasers towards Room Temperature

Student: Nicholas Saunders

Major Professor: Dr. Fisher Yu

Research Area(s):

Microelectronic-Photonic Materials & Devices

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Background/Relevance

  • Use of group IV materials for semiconductors offers many benefits compared to traditional group III-V materials.
  • GeSn has a direct bandgap above 8% Sn composition, making it ideal for use in optoelectronic devices.
  • GeSn is complementary metal-oxide-semiconductor (CMOS) compatible and has potential applications in infrared imaging and light detection and ranging (LIDAR) technology.

Innovation

  • Electrically injected GeSn lasers have not yet been extensively researched. Higher operating temperatures for such devices are desired in order to increase use in applications.

Approach

  • A PIN-doped GeSn wafer was prepared by chemical vapor deposition and wet etching.
  • Electrodes were deposited and wire bonded to a Si carrier chip to form a PIN-diode.
  • The sample was electrically injected using a pulsed voltage source.
  • Electroluminescence (EL) was measured using Fourier-transform IR spectroscopy.
  • Light output v. current (LI) curves were generated at various temperatures and used to determine the lasing threshold.

Key Results

  • The PIN-diode successfully exhibited rectification.
  • The EL spectrum shows that the device lases at a wavelength of 2688 nm at the maximum temperature.
  • Lasing occurred at temperatures as high as 135 K.
  • The LI curve shows a threshold current density of 701 A/cm2 at 77 K. The threshold current density at 135 K is 2813 A/cm2.

Conclusions

  • The device successfully lased at mid-IR wavelengths.

  • The maximum operating temperature of the GeSn PIN-diode device was measured to be 135 K, beating the previous world record by 25 K.

  • Alterations in material growth and device structure need to be studied in order to further increase operating temperature. Room temperature use is desired.

  • High power eye safe mid-IR wavelengths of light can be generated by GeSn lasers. One potential application of such a device is in LIDAR technologies.