Rutgers, The State University of New Jersey

University of Medicine and Dentistry of New Jersey

Nuri William Emanetoglu

Yicheng Lu

Sriram Muthukumar

Haifeng Sheng

Jian Zhong

Masayori Inouye

Oleg Mirochnitchenko

Shaohua Liang

Zheng Zhang

In the present invention, there is provided semiconductor devices such as a Schottky UV photodetector fabricated on n-type ZnO and MgZnO epitaxial films. The ZnO and MgZnO films are grown on R-plane sapphire substrates and the Schottky diodes are fabricated on the ZnO and MgZnO films using silver and aluminum as Schottky and ohmic contact metals, respectively. The Schottky diodes have circular patterns, where the inner circle is the Schottky contact, and the outside ring is the ohmic contact. Ag Schottky contact patterns are fabricated using standard liftoff techniques, while the Al ohmic contact patterns are formed using wet chemical etching. These detectors show low frequency photoresponsivity, high speed photoresponse, lower leakage current and low noise performance as compared to their photoconductive counterparts. This invention is also applicable to optical modulators, Metal Semiconductor Field Effect Transistors (MESFETs) and more.

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In the present invention, there are provided self-assembled ZnO nanotips grown on relatively low temperatures on various substrates by metalorganic chemical vapor deposition (MOCVD). The ZnO nanotips are made at relatively low temperatures, giving ZnO a unique advantage over other wide bandgap semiconductors such as GaN and SiC. The nanotips have controlled uniform size, distribution and orientation. These ZnO nanotips are of single crystal quality, show n-type conductivity and have good optical properties. Selective growth of ZnO nanotips also has been realized on patterned (100) silicon on r-sapphire (SOS), and amorphous SiOon r-sapphire substrates. Self-assembled ZnO nanotips can also be selectively grown on patterned layers or islands made of a semiconductor, an insulator or a metal deposited on R-plane (01{overscore (1)}2) AlOsubstrates as long as the ZnO grows in a columnar stucture along the c-axis [0001] of ZnO on these materials. Such self-assembled ZnO nanotips and nanotip arrays are promising for applications in field emission displays and electron emission sources, photonic bandgap devices, near-field microscopy, UV optoelectronics, and bio-chemical sensors.

Zinc oxide nanotip and fabricating method thereof

The present invention provides the multifunctional biological and biochemical sensor technology based on ZnO nanostructures. The ZnO nanotips serve as strong DNA or protein molecule binding sites to enhance the immobilization. Patterned ZnO nanotips are used to provide conductivity-based biosensors. Patterned ZnO nanotips are also used as the gate for field-effect transistor (FET) type sensors. Patterned ZnO nanotips are integrated with SAW or BAW based biosensors. These ZnO nanotip based devices operate in multimodal operation combining electrical, acoustic and optical sensing mechanisms. The multifunctional biosensors can be arrayed and combined into one biochip, which will enhance the sensitivity and accuracy of biological and biochemical detection due to strong immobilization and multimodal operation capability. Such biological and biochemical sensor technology are useful in detection of RNA-DNA, DNA-DNA, protein-protein, protein-DNA and protein-small molecules interaction. It can be further applied for drug discovery, and for environmental monitoring and protection.

Multifunctional biosensor based on ZnO nanostructures

Schottky diode with silver layer contacting the ZnO and MgxZn1-xO films

The present invention provides magnesium zinc oxide (Mg Zn O) as a new piezoelectric material, which is formed by alloying ZnO and MgO. Mg Zn O allows for flexibility in thin film SAW and BAW device design, as its piezoelectric properties can be tailored by controlling the Mg content, as well as by using Mg Zn O/ZnO multilayer structures. To experimentally prove it, the Mg Zn O (x&lE;0.35) thin films are grown on r-plane sapphire substrates at a temperature in the range of 400&deg; C.-500&deg; C. by metalorganic chemical vapor deposition. Mg Zn O films with Mg mole percent up to 0.35 have epitaxial quality and wurtzite crystal structure. The SAW properties, including velocity dispersion and piezoelectric coupling, are characterized and concluded that the acoustic velocity increases, whereas the piezoelectric coupling decreases with increasing Mg mole percent in piezoelectric Mg Zn O films.

Tailoring piezoelectric properties using MgxZn1-xO/ZnO material and MgxZn1-xO/ZnO structures

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 Zn O quantum well structure and piezoelectric ZnO thin film epitaxially grown on R-plane sapphire ((01{overscore (1)}2)Al O ) 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-(Al O ) 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 &ldquo;resettable&rdquo; sensing mechanism. The multiple acoustic wave modes are used for improved sensitivity and simultaneously use UV absorption measurement and SAW sensing mechanisms.

Integrated tunable surface acoustic wave technology and sensors provided thereby

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 Zn O quantum well structure and piezoelectric ZnO thin film epitaxially grown on R-plane sapphire ((01{overscore (1)}2)Al O ) 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 ( DEG) 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-(Al O ) 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 &ldquo;resettable&rdquo; sensing mechanism. The multiple acoustic wave modes are used for improved sensitivity and simultaneously use UV absorption measurement and SAW sensing mechanisms.

A ZnO monolithically integrated tunable surface acoustic wave (MITSAW) device uses tunable acousto-electric and acouso-optic interaction between surface acoustic waves (SAW) and a two dimensional electron gas (2DEG) in a ZnO/Mg Zn O quantum well. The high electromechanical coupling coefficients of piezoelectric ZnO in conjunction with the low acoustic loss and high velocity of sapphire (Al O ) offers high frequency and low loss RF applications. The 2DEG 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&mdash;(Al O ) systems allows large velocity tuning. Combined with the optical characteristics of the wide and direct band gap (about 3.3 eV) semiconductor and transparent ZnO electrodes, the MITSAW chip can be used for UV optical signal processing. R-plane sapphire is chosen instead of the popular C-plane substrate, as this substrate provides in-plane anisotropy in the ZnO layer. ZnO MITSAW technology not only improves existing devices but also develops many important application areas, such as tunable/adaptive filters, voltage-controlled oscillators, zero-power remote wireless sensors, and fixed and tunable UV optical delay lines.

Growing community of inventors

Woodbury, NJ, United States of America

Nuri William Emanetoglu