Molecular beam epitaxy of GaNAs alloys with high As content for potential photoanode applications in hydrogen production

作者：Novikov S V^*; Staddon C R; Foxon C T; Yu K M; Broesler R; Hawkridge M; Liliental Weber Z; Walukiewicz W; Denlinger J; Demchenko I

来源：JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B, 2010, 28(3): C3B12-C3B16.

DOI：10.1116/1.3368600

• aluminium compounds
• amorphous state
• energy gap
• gallium compounds
• III-V semiconductors
• molecular beam epitaxial growth
• plasma materials processing
• semiconductor growth
• transmission electron microscopy
• X-ray absorption
• X-ray emission spectra
• X-ray microscopy

The authors have succeeded in growing GaN1-xAsx alloys over a large composition range (0 < x < 0.8) by plasma-assisted molecular beam epitaxy. The enhanced incorporation of As was achieved by growing the films with high As-2 flux at low (as low as 100 degrees C) growth temperatures, which is much below the normal GaN growth temperature range. Using x-ray and transmission electron microscopy, they found that the GaNAs alloys with high As content x>0.17 are amorphous. Optical absorption measurements together with x-ray absorption and emission spectroscopy results reveal a continuous gradual decrease in band gap from similar to 3.4 to < 1 eV with increasing As content. The energy gap reaches its minimum of similar to 0.8 eV at x similar to 0.8. The composition dependence of the band gap of the crystalline GaN1-xAsx alloys follows the prediction of the band anticrossing model (BAC). However, our measured band gap of amorphous GaN1-xAsx with 0.3 < x < 0.8 are larger than that predicted by BAC. The results seem to indicate that for this composition range the amorphous GaN1-xAsx alloys have short-range ordering that resembles random crystalline GaN1-xAsx alloys. They have demonstrated the possibility of the growth of amorphous GaN1-xAsx layers with variable As content on glass substrates.

• 出版日期2010-5