Achieve low-cost introduction of source gases such as CBr4 and NH3 for MBE systems with Veeco’s Low Temperature Gas Source. This unit features a large conductance tube for fast gas switching and a diffuser end plate for good growth uniformity. It is ideal for source gases that do not require thermal pre-cracking before reaching the substrate. Enhance MBE process flexibility and yield by combining this source on one mounting flange with an Atomic Hydrogen Source or a conical Dopant Source.

• Introduces gas without thermal pre-cracking
• Ammonia source for nitride growth
• Ideal injector for organometallic materials
• More than 50 in the field

The 91ÖÆƬ³§Low Temperature Gas Source for MBE systems provides a low-cost means to introduce a source gas without thermal pre-cracking. The source features a large conductance tube for fast gas switching and a diffuser end plate for good growth uniformity. With advanced flux modeling, the end plate hole pattern is customized to the specific MBE system for optimal performance. A band heater, external to vacuum, heats the source to a temperature range (< 200°C) sufficient to prevent condensation of the gas in the tube, yet not high enough to promote cracking.

To make efficient use of the source ports on an MBE system, this source may be combined on a single mounting flange with the Atomic Hydrogen Source, or a conical Dopant Source. For these combination sources, the gas injector does not include a separate band heater, but rather is heated by the source or hydrogen-cracking filament.

Performance and Benefits

This source is an ideal gas injector for these applications:

• NH3 for GaN growth
• CBr4 for C doping
• Any other desired source gases that do not require thermal pre-cracking before reaching the substrate
• Optimized beam flux for minimizing gas load to system with good uniformity

MBE growers use a variety of active nitrogen sources for deposition of GaN and other nitride-containing materials. While highly stable N2 source gas must be activated in a plasma, NH3 is sufficiently reactive for deposition even without thermal pre-cracking. The Low Temperature Gas Source is ideal for injection of NH3 into the growth chamber. The conductance tube is heated sufficiently (<200°C) to prevent condensation without providing any cracking of the source gas. Typical substrate temperatures, in the range of 700–900°C, are sufficient to cause dissociation of the NH3 directly at the substrate.

Get optimal conditions for GaN growth of electronic and optoelectronic materials, plus unrivaled plasma stability and reproducibility, with Veeco’s Uni-Bulb RF Plasma Source. One-piece PBN gas inlet tube and plasma bulb combines with dual coaxial RF coil for excellent power coupling and heat removal. Several design options, including customized aperture plates, are available to enhance performance further.

A gas plasma is an effective tool for conversion of highly stable source gases such as N2 or H2 to more active atomic and molecular species suitable for MBE growth. The 91ÖÆƬ³§UNI-Bulb features a patented one-piece PBN gas inlet tube and plasma bulb to eliminate gas leakage around the bulb. The resulting plasma is highly stable and reproducible, allowing many hours of run time without source re-tuning.

Interchangeable aperture plates are available in configurations of varying gas conductance for growth of GaN, mixed As/N materials, nitrogen doping, hydrogen cleaning and hydrogen assisted growth. The exit hole design minimizes ion content in the beam, while the active neutral species (atomic and molecular) are directed toward the substrate. Customized high uniformity aperture plates are available for most commercial MBE systems enabling typical uniformity of ±1%.

• Patented design with more than 225 in the field
• All-PBN, oxide-free plasma bulb construction
• Optimized exit aperture minimizes ion content and provides excellent film uniformity
• Excellent plasma stability and reproducibility
• Configurations available for growth of GaN, mixed nitrides, N doping, hydrogen cleaning and hydrogen assisted growth
• Autotuner option ensures stable growth conditions and optimizes power efficiencies

Performance and Benefits

The 91ÖÆƬ³§UNI-Bulb RF Plasma Source is the world’s most popular for nitride growth by MBE. It provides optimal conditions for nitride growth, as proven by its record-setting results for electronic and optoelectronic applications.

These include:

• Record low threshold currents for 1.32μm GaInNAs/GaAs quantum well lasers (Tampere University of Technology, 2001)
• Production of 1.26μm InGaAsN VCSELs compatible with telecom network requirements (Cielo Communications and Sandia National Laboratories, 2001)
• Growth of AlGaN/GaN two-dimensional electron gas structures with record high mobility’s of 160,000cm2/Vsec at 77K and 51,700cm2/Vsec at 13K (University of California, Santa Barbara, 1999)
• PI-HEMTs from AlGaN/GaN show small signal RF performance and DC breakdowns as a function of gate length that are as good as the best transistors made by MOVPE (Cornell University, 1999)
• Reported GaN growth rates as high as 2.6μm/hr. (University of Tokyo, 1999). Most commonly, the source is used for GaN growth rates in the range of 0.8-1.0μm/hr
• Mass spectroscopy studies indicate that the beam flux is rich in metastable nitrogen molecules with very low ion content. The metastable molecules exhibit a high incorporation rate in GaN growth and stabilize the growth rate at high substrate temperatures (approx. 700-750°C.) (West Virginia University, 1999)

For high-performance UHV delivery of gases requiring thermal cracking before arriving at the substrate in MBE applications, Veeco’s Gas Crackers offer unique features like a customized exit cone and endplate to optimize flux uniformity. These gas crackers feature a conventional single filament source heater for radiative heating of the tantalum or PBN cracking tube. Multiple design options to enhance process efficiency are also available.

• For UHV delivery of gases requiring thermal cracking
• Ta or PBN gas conductance tube
• Excellent uniformity with customized exit cone and endplate
• More than 40 in the field

Gas crackers are used with source gases that must be activated by thermal cracking before arriving at the substrate. Gas crackers feature a conventional single filament source heater for radiative heating of the tantalum or PBN cracking tube. An internal baffle may be used to enhance cracking efficiency. Sources are available with multiple gas inlets, as well as up to three separate conductance tubes.

Veeco’s retractable sources address fundamental limitations of MBE, including source capacity, source removal for maintenance and system uptime. The retractable source allows an individual source to be withdrawn and isolated from the growth environment with the source gate valve and then removed without venting the entire chamber. The source can then be easily refilled with the same material or a new material before being remounted at standard positions to the growth module, allowing growths to continue with minimal interruption. This saves the user from re-qualifying new source to substrate distances and multiple weeks of downtime by avoiding the process of an entire system vent and bake. In addition, the differential pumping option provides a marked improvement in base pressure around the source to reduce contamination of the source material and provide longer lifetimes for sources in corrosive and oxidizing environments. Veeco’s retractable source is the leading solution for material flexibility, system productivity and enhances our leadership with the patented SUMO source technology.

• Provides virtually uninterrupted system operation
• Reduces refill and maintenance times
• Improves reliability and bellows-free design
• Preserves purity of source material via differential pumping
• Available exclusively on 91ÖÆƬ³§MBE systems

Get rapid, reliable high temperature thermal cracking of H2 into Atomic H for molecular beam epitaxy (MBE) from the 91ÖÆƬ³§Atom-H Source. This all-refractory metal source is designed for operation at 1800-2200°C and is compatible with most preparation and growth chambers. Besides high-temperature MBE, Atomic H has been shown to be ideal for low temperature in-situ substrate cleaning and for structure overgrowth preparation.

• Specialized high-temperature thermal cracker for cracking H2 into atomic H—useful in substrate cleaning and during MBE growth
• Tungsten heater filament positioned inside the gas conductance tube for operation at 1800-2200°C
• Available on 2.75″/70mm water-cooled Cf mounting flange for compatibility with most preparation and growth chambers
• Well-suited for low temperature in-situ substrate cleaning and preparing structures for overgrowth
• Applications include promotion of two-dimensional GaAs growth, GaN growth rate enhancement and selective epitaxy

Cracking Efficiency of the 91ÖÆƬ³§Atomic Hydrogen Source Atomic hydrogen has been used in solid source MBE for a variety of applications relating to epitaxy and substrate cleaning. Many of the reported results have been achieved using thermally cracked H2 generated by home-built cracker sources.

Achieve precise MBE operation at medium temperatures and partial pressures, plus increased campaign time and lower repair costs, with 91ÖÆƬ³§oxygen-resistant, extended life sources. Options include substrate heaters for high oxygen partial pressures and the SUMO crucible for optimal flux distribution and minimized depletion effects.

• Extended life for oxygen environments
• SUMO crucible available with optimal flux distribution and minimized depletion effects
• Oxygen partial pressures up to 5milliTorr
• Temperatures up to 1150°C
• More than 20 in the field

Oxide material research has increased considerably over the years because of its importance in the IC industry and because of the wide variety of electronic and optical properties made possible using these materials.

Due to the corrosive nature of oxygen, performing thin-film research in an oxygen environment often presents equipment challenges. For example, it is common to thermally evaporate materials in an oxygen environment of 10-5 Torr or higher while maintaining the substrate temperature at 800°C. The high oxygen partial pressure and temperature greatly reduces the lifetime of the heating elements in sources and substrate heaters. As a result, the equipment uptime is compromised, leading to shorter campaign lengths and high repair costs.

Using special oxygen-resistant materials as opposed to traditional materials such as molybdenum and tantalum, it is now possible to operate Veeco’s innovative and proven sources and substrate heaters in high oxygen partial pressure environments. Oxygen-resistant sources are currently available from 91ÖÆƬ³§for temperatures up to 1150°C with oxygen partial pressures as high as 5milliTorr. Substrate heaters are also available for temperatures up to 800°C and oxygen partial pressures of 5milliTorr.