1 / 24

Measurements of the E-field Breakdown and Band Offsets of SiO 2 on GaN

Measurements of the E-field Breakdown and Band Offsets of SiO 2 on GaN. Ted Cook, Ed Hurt, Kieran Tracy, R.F. Davis, G. Lucovsky, and R.J. Nemanich North Carolina State University Raleigh, NC 27695-8202 USA February 12, 2002. Introduction.

chaka
Télécharger la présentation

Measurements of the E-field Breakdown and Band Offsets of SiO 2 on GaN

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Measurements of the E-field Breakdown and Band Offsets of SiO2 on GaN Ted Cook, Ed Hurt, Kieran Tracy, R.F. Davis, G. Lucovsky, and R.J. Nemanich North Carolina State University Raleigh, NC 27695-8202 USA February 12, 2002

  2. Introduction • The band offsets have a direct effect on the properties of the interface, and therefore affect the reliability and stability of the device • Investigation of the band offsets, as well as their effects, such as E-field breakdown, is important for device fabrication, and will be explored in this study

  3. Goal and Motivation Goal: • Measure the Valence Band Offsets between atomically clean GaN and SiO2 using photoemission techniques Motivation: • Passivation of high voltage devices • Wafer Bonding – fusion bonded interfaces • Gate insulator applications

  4. Experimental Procedure • Achieve atomically clean GaN surface using CVC anneal in NH3 atmosphere @ 860°C for 15 minutes • XPS and UPS performed after each of the following steps to track the evolution of peak shifts • Deposition of 2Å Si via MBE • Deposition of a second 2Å Si layer • Oxidation of Si layer using a Remote O2 plasma • Deposition of 2Å, and oxidation of the Si layer • 650°C anneal for 15 minutes to densify the oxide • Deposition of 3Å, and oxidation of the Silicon layer • Final anneal at 650°C for densification

  5. Integrated UHV Surface and Interface Processing System LoadLock Field Emission ECR N2 Plasma Wafer Bonding Si-Ge MBE ARUPS XPS GSMBE High Voltage Testing CVD Diamond AES / LEED e-beam evap Hydrogen/Oxygen Plasma

  6. Proposed Valence Band Line-up between n-GaN and SiO2 6.0 Ef 5.5 Ec 5.0 Ev 4.5 c = 1.1eV Evac 4.0 3.5 3.0 2.5 Ec-Ef = 3.70eV 2.0 c = 2.9eV D Ec = 3.6eV 1.5 1.0 Ec-Ef =0.08eV 0.5 0.0 Eg = 9.0eV -0.5 -1.0 Ed = 0.3eV -1.5 E g = 3.40eV Ef-Ev = 3.32eV -2.0 Ef-Ev = 5.30eV -2.5 -3.0 -3.5 -4.0 D Ev = 2.0eV -4.5 -5.0 -5.5 GaN SiO2 -6.0 Clean

  7. Gallium 3d XPS Evolution of n-type GaN

  8. Energy Band Diagram CB CB Ef Ef VB VB Clean GaN Surface Final Surface

  9. UPS Spectra of VB turn-on 0.3 eV shift due to band bending

  10. Valence Band Offset between GaN and SiO2 6.0 Ef 5.5 Ec 5.0 Ev 4.5 c = 1.1eV Evac 4.0 3.5 3.0 2.5 Ec-Ef = 3.70eV 2.0 c = 2.9eV D Ec = 3.6eV 1.5 1.0 Ec-Ef =0.08eV 0.5 0.0 Eg = 9.0eV -0.5 -1.0 Ed = 0.3eV -1.5 E g = 3.40eV Ef-Ev = 3.32eV -2.0 Ef-Ev = 5.30eV -2.5 -3.0 -3.5 -4.0 D Ev = 2.0eV -4.5 -5.0 -5.5 GaN SiO2 -6.0 Clean

  11. Oxygen 1s XPS Spectra showing Oxide Formation

  12. UPS Spectra of Spectral Width W=11.1 eV Eg SiO2 =9.0 eV c=21.2-11.1-9.0 = 1.1 eV c=hn-W-Eg c=21.2-14.9-3.4 = 2.9 eV Eg GaN =3.4 eV W=14.9 eV

  13. Electron Affinity difference between GaN and SiO2 6.0 Ef 5.5 Ec 5.0 Ev 4.5 c = 1.1eV Evac 4.0 3.5 3.0 2.5 Ec-Ef = 3.70eV 2.0 c = 2.9eV D Ec = 3.6eV 1.5 1.0 Ec-Ef =0.08eV 0.5 0.0 Eg = 9.0eV -0.5 -1.0 Ed = 0.3eV -1.5 E g = 3.40eV Ef-Ev = 3.32eV -2.0 Ef-Ev = 5.30eV -2.5 -3.0 -3.5 -4.0 D Ev = 2.0eV -4.5 -5.0 -5.5 GaN SiO2 -6.0 Clean

  14. Models of Heterojunctions EAM IDM • Electron Affinity Model Valid if small or no change in the interface Dipole • Interface Dipole Model Change in the Electric field at interface • Deviation from the electron affinity of the heterojunction alignment represents the interface dipole

  15. Interface Dipole in Band Line-up of GaN and SiO2 6.0 Ef 5.5 Ec 5.0 Ev 4.5 c = 1.1eV Evac 4.0 3.5 3.0 2.5 Ec-Ef = 3.70eV 2.0 c = 2.9eV D Ec = 3.6eV 1.5 1.0 Ec-Ef =0.08eV 0.5 0.0 Eg = 9.0eV -0.5 -1.0 Ed = 0.3eV -1.5 E g = 3.40eV Ef-Ev = 3.32eV -2.0 Ef-Ev = 5.30eV -2.5 -3.0 -3.5 -4.0 D Ev = 2.0eV -4.5 -5.0 -5.5 GaN SiO2 -6.0 Clean D=1.9 eV

  16. Conclusions for n-type experiment • Special care has been taken to prevent oxidation of gallium • Band bending of ~0.3 eV for CVC GaN surface • Electron Affinity ~2.9 eV for CVC GaN surface • Flat Bands at the GaN-SiO2 Interface • Valence Band Offset of ~2 eV for GaN-SiO2 for  1x1017cm-3 n-type GaN • Conduction Band offset of ~3.6 eV for GaN-SiO2 assuming EgSiO2 =9.0 eV • Deviation from the Electron Affinity model due to Interface dipole of ~1.9 eV

  17. Gallium 3d XPS Evolution of p-type GaN

  18. Proposed Valence Band Line-up between p-GaN and SiO2 6.0 Ef 5.5 Ec 5.0 Ev 4.5 Evac 4.0 3.5 3.0 2.5 Ec = 3.3eV Ec-Ef =3.1eV E = 3.40eV 2.0 g 1.5 Ec-Ef = 4.5eV 1.0 EB=0.3eV 0.5 0.0 -0.5 Eg = 9.0eV Ef-Ev = 4.5eV Ef-Ev=1.7eV -1.0 Ef-Ev = 2.2eV -1.5 -2.0 -2.5 -3.0 Ev = 2.3eV -3.5 -4.0 -4.5 -5.0 Clean GaN SiO2 -5.5 -6.0

  19. Conclusions for p-type experiment • Initial Band Bending of 1.4 eV for CVC GaN surface • Additional downward Band Bending of ~0.5 eV as the surface was formed • Valence Band offset of ~2.3 eV for GaN-SiO2 for 2x1018 cm-3 p-type GaN • Conduction Band Offset of 3.3 eV for GaN-SiO2 assuming Eg Sio2 =9.0 eV

  20. E-field Breakdown Procedure • Achieve atomically clean GaN surface using CVC anneal in NH3 atmosphere @ 860°C for 15 minutes • Deposit 4Å Si via MBE on surface to help prevent oxidation of the Gallium • Deposit 300Å SiO2 via Remote O2 Plasma • Anneal to 650°C to densify the oxide • Form 0.068 mm2 Al contacts on the surface using photolithographic techniques • Electrical characterization of sample

  21. Device Structure for Electrical Testing Al Contacts V SiO2 GaN AlN SiC W Contact I CRT v

  22. Breakdown Frequency 300Å SiO2 unintentionally doped, n-type <1.0x1017 cm-3

  23. Conclusions • These high values of breakdown voltage lends to the notion that the GaN layer is having an insulating effect • A full understanding of this effect requires more study • Film deposition rate of 2.5 Å/min established; verified by ellipsometry and C-V measurements

  24. Future Work • Reduce Band Bending for p-type GaN/SiO2 -Improve cleaning methods -Oxide integrity • Effect of different passivation layers • Si3N4 • High k dielectrics

More Related