Single Crystal Diamond Schottky Photodiode
Single Crystal Diamond Schottky Photodiode
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单晶金刚石肖特基光电二极管
DOI：
10.5772/18471
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发表时间：
2011
期刊：
影响因子：
--
通讯作者：
C. Verona
中科院分区：
文献类型：
--
作者：
C. Verona
由于其极端的光学和电学性质，金刚石似乎是一种很有前途的光子探测半导体材料。它的带隙很宽，5.5 eV，导致了非常低的泄漏电流，并且它的高载流子迁移率的电子特性允许快速的时间响应(J.E.菲尔德，1979)。此外，它具有很大的击穿电场(∼10V/┤m)、低介电常数(即低电容)、化学惰性和低本征载流子密度，这使得不需要通过冷却来降低噪音(J.Prins，1997年)。它的极高的辐射硬度是众所周知的，另一个有趣的特征，也与宽带隙有关，是它对波长小于225 nm的辐射的选择性敏感性(可见光盲探测器)(J.F.Hochedez等人，2002年)。人们曾多次尝试从化学气相沉积(CVD)生长的天然或合成钻石中建立紫外线探测器。文献中经常报道的一种检测器是具有平面结构的光敏电阻(A.Balducci等人，2005；T.Teraji等人，2004)，并由顶部表面放置有金属电极的光导金刚石膜组成。它只能在外加电压的情况下工作，并且信号受到二次电子发射的影响，这是众所周知的，这强烈地影响了UV和EUV光谱区域的探测性能。已报道的一种不同的几何结构是多晶夹层光电二极管结构(VI.Polyakov等人，1998，L.Thaiyotin等人，2002)，在钻石生长表面上具有触点，在硅衬底上具有背面触点。然而，在这种情况下，CVD金刚石的性能受到多晶结构的限制，这是由于晶界在带隙中引入的缺陷态(R.D.McKeag&R.B.Jackman，1998，L.Barberini，2001)，这影响了光电性能并改变了检测特性。另一方面，探测器级天然钻石极其稀有和昂贵，而高压高温钻石的性能因缺陷和杂质而严重恶化(E.Pace et a.，2000)。因此，人们正致力于通过在低成本的金刚石衬底上同质外延CVD生长来生产器件级的单晶金刚石薄膜(S.Almaviva等人，2009,2010a)。几年前，在罗马大学的Tor Vergata实验室，CVD单晶金刚石薄膜被用来获得一类具有层状结构的新型探测器。由于掺硼单晶金刚石薄膜和本征单晶金刚石薄膜的结合，以及通过热蒸发金属接触在本征金刚石上轻松建立肖特基结的可能性，通过使用简单的多层p型/名义上本征金刚石/金属层状结构，已经有可能获得高质量和高重复性的器件，这些器件可以有效地用于探测(紫外线和X射线)光子。
Thanks to its extreme optical and electronic properties, diamond appears to be a promising semiconducting material for photon detection. Its wide band-gap, 5.5 eV, results in a very low leakage current and its electronic properties as high carrier mobility allow fast time response (J. E. Field, 1979). Besides, it has a large breakdown electric field (∼10 V/┤m), a low dielectric constant (i.e. low capacitance), chemical inertness and low intrinsic carrier density, which makes cooling for noise reduction unnecessary (J.Prins, 1997). Its extreme radiation hardness is well known and another interesting feature, again related to the wide band-gap, is its selective sensitivity to radiation with wavelengths shorter than 225 nm (visible-blind detectors) (J.F. Hochedez et al., 2002). Several attempts have been made to build up UV detectors from natural or synthetic diamonds grown by Chemical Vapour Deposition (CVD). A detector often reported in literature is the photoresistor (A. Balducci e al., 2005; T. Teraji et al., 2004) having a planar structure and consisting of a photoconductive diamond film with metal electrodes placed on the top surface. It can operate only with external voltage applied and the signal is affected from secondary electron emission, which is known to strongly affect the detection properties in the UV and EUV spectral regions. A different geometry reported is a polycrystalline sandwiched photodiode structure (V.I. Polyakov et al., 1998, L. Thaiyotin et al., 2002) with a contact on the diamond growth surface and a backside contact on the silicon substrate. However, the CVD diamond performance is limited in this case by the polycrystalline structure due to defect states in the band gap introduced by the grain boundaries (R. D. McKeag&R. B. Jackman, 1998, L. Barberini, 2001), which affects the photoelectric properties and alters the detection characteristics. On the other hand, detector grade natural diamonds are extremely rare and expensive, while high pressure high temperature (HPHT) diamonds have their performance strongly worsened by defects and impurities (E. Pace et a., 2000). A great effort is therefore being devoted to produce device-grade Single Crystal Diamond films (SCD) by homoepitaxial CVD growth on low-cost diamond substrates (S. Almaviva et al., 2009, 2010a). A few years ago, at the University of Rome “Tor Vergata” laboratories, CVD single crystal diamond films were used to obtain a new class of detectors with a layered structure. Thanks to the combination of boron doped and intrinsic single crystal diamond films, together with the possibility to easily build Schottky junctions on intrinsic diamond by thermal evaporation of the metal contacts, it has been possible, by using simple multilayered a p-type/nominally intrinsic diamond/metal layered structures, to obtain high quality and highly reproducible devices which can be effectively used for detection (UV and X-rays) photons.