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10 November 2006


New arsenic cracker source for MBE

The new EcellAs valved arsenic effusion source or ‘cracker cell’ from Oxford Instruments is designed for high-performance MBE growth of arsenic-containing III-V materials. Large crucible capacity, fast and precise flux control, and easy, modular handling for maintenance and crucible refill make it equally suited to production and high-throughput development systems, in addition to research reactors, with the desired throughput and campaign length achievable via 1l, 3l and 8.5l versions.

The EcellAs offers high-reliability and easy maintenance: a frequent problem of valved cracker cells, that of valve clogging, is prevented by a unique patented independent heater design. For easy on-site maintenance and service, the unique construction allows the reservoir to be individually demounted from the cracker unit, minimizing system down-time and removing the need to replace the complete cell or return it for factory service. A heated secondary filling port allows As recharge without needing to empty the crucible first.

“The EcellAs offers very significant benefits in terms of cost of ownership and reduced downtime to users of our MBE systems [the V80H, V90 and V100] and those of other vendors,” says Tony Cornish, business manager for MBE and Ion Beam products. “Excellent control over MBE growth processes has been demonstrated, with rapid, linear valve response, highly controllable As4 to As2 transition and fast, repeatable As flux modulation.”

The EcellAs reservoir heater design gives the flexibility to mount the cell in any orientation. Complete automated control is offered via a motorized valve and growth software interface.

Valved effusion sources or cracker cells offer significant benefits over the thermal control of conventional open sources for MBE: a needle valve provides optimized control
over the growth process with precise, fast flux modulations and complete flux shut-off, which allows the As source to be left continuously at operating temperature without depleting charge material. The As charge capacity may be indiscriminately large without limiting the responsiveness of the source; whether using the 1 l or 8.5 l versions, As flux responsiveness remains constant.