Details

Autor(en) / Beteiligte

• Marini, Jonathan
• Mahaboob, Isra
• Rocco, Emma
• Bell, L. D.
• Shahedipour-Sandvik, F.

Titel

Polarization engineered N-polar Cs-free GaN photocathodes

Ist Teil von

• Journal of applied physics, 2018-09, Vol.124 (11)

Ort / Verlag

Melville: American Institute of Physics

Erscheinungsjahr

2018

Quelle

American Institute of Physics (AIP) Journals

Beschreibungen/Notizen

• We report on holistic and systemic approach of development of Cs-free GaN photocathode structures which utilize polarization band engineering in order to allow for air stable operation and eliminate the need for cesium-based surface treatments. Physics-based simulation of band structure and Monte Carlo simulation of electron transport and emission were used to guide experimental development of photocathode structures. By using an N-polar device, the polarization charge allows for the creation of large surface band bending without the need for δ-doped capping layers. The insertion of a thin AlN interlayer allows for the creation of a quasi-band offset and additional beneficial polarization charge to create a desirable band profile. Samples of both polarities were grown and subjected to chemical surface treatments in order to account for differences in native oxide formation on Ga- and N-polar surfaces. Measured photoemission spectra show quantum efficiencies as high as 23% for a HCl-treated Cs-free N-polar photocathode, which is comparable to cesiated devices.