【分子束磊晶蓝光雷射再获突破】

t0y · 发表于 2008-2-24 17:38:40

目前所有商用蓝紫外光雷射二极管(laser diode)都是以金氧化学气相沈积(MOCVD)法成长；去年初，夏普(Sharp)公司在英国实验室的JonHeffernan等人首次以分子束磊晶法，制作出波长405 nm雷射二极管，然而最初这些组件仅能以脉冲方式工作，且临界电流非常高。若要应用于商业上，这些雷射势必要能连续操作，且功率要够大才能读取光盘上的资料。现在，该小组终于以分子束磊晶法，制作出连续发光的氮化铟镓(InGaN)蓝光雷射二极管。

Heffernan认为此举证实了MBE确实是可用于氮化物雷射的成长技术，而夏普是目前唯一同时拥有MBE和MOCVD技术的领先者。该小组最新研发的雷射在室温下可以约0.2mW的发射功率，以连续波模式操作三分钟，整片晶圆中雷射二极管激发的中心波长为405 nm，其变动范围在6 nm内。连续波模式下的临界电流为125 mA，对应的临界电流密度为5.7kA/cm2。

Heffernan等人是在N型GaN基材上制作上述雷射，且活化区包含三层厚度3 nm之未掺杂InxGa1-xN(x=10%)量子井。与MOCVD法相较，以MBE来生长雷射二极管，不需使用氨气来制作氮成份，因此可以降低制造成本。

在进一步将MBE导入量产之前，Heffernan等人仍有许多研发工作要进行。该小组目前郑在研究如何藉由AlGaN被覆层中的P型?杂的最佳化，以及降低成长温度，来改进组件的操作特性，并增长组件寿命。

值得一提的是，夏普的横滨厂早已经在使用MBE量产全世界大部分的DVD用红光雷射。夏普与其它的发展蓝光雷射的制造商如日亚(Nichia)、新力(Sony)及MatsushitaElectric同属于蓝光光盘协会(Blu-ray Disc Association)的成员。

MBE blue lasers take the next stepSharp's European research wing has made continuous-wave blue laser diodes using MBE growth.

Engineers at Sharp’s research laboratory in the UK have fabricatedthe first continuous-wave InGaN-based laser diodes to be grown by MBE.

At room temperature, the Sharp team’s latest lasers emitted around 0.2 mW for three minutes before burning out.

All commercial blue-violet laser diodes are grown by MOCVDcurrently, but early last year Jon Heffernan and colleagues at SharpLaboratories Europe produced 405 nm diodes using MBE for the first time(see related story).

However, those initial devices only worked in pulsed mode and had avery high threshold current. To be used commercially, the lasers needto work continuously and at sufficient power to read data on opticaldiscs.

“This result confirms that MBE is a viable growth method for nitridelasers,” said Heffernan. “Sharp is now in the unique position of havingboth MBE and MOCVD technologies available.”

At room temperature, the Sharp team’s latest lasers emitted around0.2 mW for three minutes before burning out. The continuous-wavethreshold current was 125 mA, corresponding to a threshold currentdensity of 5.7 kAcm-2, reports the team in the June 23 issue of the journal Electronics Letters.

Heffernan and colleagues made the lasers on n-type GaN substratessupplied by Sumitomo Electric Industries. The active laser regionincluded three undoped 3 nm-thick InGaN quantum wells with 10% indiumfraction.

The lasers operated in continuous-wave mode for around threeminutes, and across the wafer there was a variation of around 6 nmabout the crucial emission wavelength of 405 nm.

Growing the lasers by MBE rather by MOCVD promises to lowermanufacturing costs by reducing the consumption of ammonia gas, whichprovides the nitrogen content in the devices.

However, Heffernan and colleagues still have a lot of developmentwork to do before the MBE method can be considered suitable for massproduction. The team will now concentrate on improving device operatingcharacteristics by optimizing p-type doping in the AlGaN claddingregion and reducing the growth temperature, which should increase thelifetime of the devices.

Significantly, the European laboratory’s parent company already usesMBE in mass production of lasers. At its Mihara fabrication facility inHiroshima, Sharp manufactures a large proportion of the world’s redlasers that are used in DVD applications.

Sharp is also part of the Blu-ray Disc Association, along withpotential blue laser manufacturers Nichia, Sony and Matsushita Electric.

[ 本帖最后由 t0y 于 2008-2-24 17:42 编辑 ]


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【分子束磊晶蓝光雷射再获突破】

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