Integrated tunable surface acoustic wave technology and sensors provided thereby

• US 6,621,192 B2
• Filed: 07/13/2001
• Issued: 09/16/2003
• Est. Priority Date: 07/13/2000
• Status: Expired due to Fees

• Current Assignee: Rutgers University
• Original Assignee: Rutgers University
• Inventors: Lu, Yicheng, Emanetoglu, Nuri W.
• Primary Examiner(s): Budd, Mark O.
• Application Number:
  US09/905,205
• Publication Number:
  US 20020043890A1
• Time in Patent Office: 795 Days
• Field of Search: 310/313.R, 310/313.D, 310/313.A
• US Class Current: 310/313.00A
• CPC Class Codes: G01N 21/33 using ultraviolet light G01N21/39 takes precedence
• CPC Class Codes: H03H 9/02976 with semiconductor devices

Abstract

The present invention provides a ZnO based tunable surface acoustic wave (SAW), preferably monolithically integrated tunable SAW (MITSAW) device. The MITSAW comprises a ZnO/Mg_x Zn_1−xO quantum well structure and piezoelectric ZnO thin film epitaxially grown on R-plane sapphire ((01{overscore (1)}2)Al₂O₃) substrate using MOCVD. R-plane sapphire provides in-plane anisotropy in the ZnO layer as the c-axis of ZnO lies in the growth plane. A two-dimensional electron gas (2DEG) is placed in the delay path of the SAW device and interacts with the lateral electric field resulting in ohmic loss which attenuates and slows the surface acoustic wave. This mechanism is used to tune the acoustic velocity. The high coupling coefficients offered by the ZnO/R-(Al₂O₃) system allows large velocity tuning. ZnO based MITSAW is used for chemical and biochemical sensors, offers excellent manufacturability, high yield and low cost. Such SAW sensors have a “resettable” sensing mechanism. The multiple acoustic wave modes are used for improved sensitivity and simultaneously use UV absorption measurement and SAW sensing mechanisms.

Claims

1. An integrated multi-mode tunable SAW device comprising a piezoelectric member comprised of zinc oxide, a quantum well structure comprised of the zinc oxide and magnesium zinc oxide heterostructure, disposed on a first layer of said piezoelectric member, input and output IDTs disposed on a second layer of said piezoelectric member, a metal electrode disposed on said heterostructure and on said piezoelectric member, and a R-plane sapphire substrate on which said first and second layers of said piezoelectric member are disposed.

2. The integrated multi-mode tunable SAW device claimed in claim 1, wherein said electrode is a patterned metal layer controlling electron conductivity in said quantum well structure.

3. The integrated multi-mode tunable SAW device claimed in claim 1, wherein said R-plane sapphire substrate provides in-plane anisotropy in said piezoelectric member.

4. The integrated multi-mode tunable SAW device claimed in claim 1, wherein said quantum well structure comprises ZnO/Mg_xZn₁₋

xO monolithically integrated on said R-plane sapphire substrate through a crystal growth technique.

5. The integrated multi-mode tunable SAW device claimed in claim 4, wherein said crystal growth technique is MOCVD.

6. The integrated multi-mode tunable SAW device claimed in claim 1, wherein said second layer of said piezoelectric member is disposed on said quantum well structure.

7. The integrated multi-mode tunable SAW device claimed in claim 1, wherein said electrode is disposed on a SAW path of said second layer of said piezoelectric member.

8. The integrated multi-mode tunable SAW device claimed in claim 1, wherein said R-plane sapphire substrate provides high acoustic velocity in said piezoelectric member.

9. The integrated multi-mode tunable SAW device claimed in claim 1, wherein said R-plane sapphire substrate provides low lattice mismatch in said piezoelectric member.

10. The integrated multi-mode tunable SAW device claimed in claim 3 wherein waves generated in said piezoelectric member are capable of being used for gas-phase and liquid-phase sensing.

11. The integrated multi-mode tunable SAW device claimed in claim 10, wherein said waves are Rayleigh waves excited parallel to a c-axis of the zinc oxide and is used for said gas-phase sensing.

12. The integrated multi-mode tunable SAW device claimed in claim 10, wherein said waves are Love waves excited parallel to the c-axis of the zinc oxide and is used for said liquid-phase sensing.

13. The integrated multi-mode tunable SAW device claimed in claim 1, wherein said device can be simultaneously operated for SAW and UV optical sensing.