Study of Ultra High Frequency Surface Acoustic Wave Filters by the use of Diamond-cubic AIN Structure

我们在2000财年研究的课题是评价p型金刚石作为SAW衬底，以及在金刚石上生长AlN薄膜的沉积方法。分析了重掺杂p型金刚石的导电机理。金刚石是一种具有5.5 eV宽带隙能量的半导体，其导电机制与Si和GaAs的带隙能量约为1 eV不同。当杂质浓度增加时，由于杂质之间的相互作用，形成一个新的较浅的杂质能级，载流子通过这个能级移动。这一机制通过在具有杂质能带传导的重掺杂p型金刚石之间使用轻掺杂p型金刚石的夹层结构来证明(参见文献(1)、（5)和(6)）。对于AlN的沉积方法，我们研究了氮电子回旋等离子体共振点沉积和传统金属有机化学气相沉积（MOCVD）两种方法。采用MOCVD法，在1150℃的沉积温度下得到了质量较好的AlN。通过前一种方法，我们成功地在低于600℃的温度下生长出了品质优良的AlN。这种方法使我们能够在金属Al异质外延上生长出高质量的AlN。利用这种方法，我们在Al数字间换能器（IDT）上制作了AlN SAW滤波器，在制作的SAW滤波器处得到了300万的品质因子。这种高质量因素被认为是由于均匀厚度的氮化铝薄膜中的兰姆波激发。在名古屋举行的国际氮化物研讨会（IWN 2000）上报道了这一结果（见参考文献（2,3））。为了评估我们的声表面波滤波器的计算机模拟效果，我们利用生长在蓝宝石c面和r面上的AlN制作了几个声表面波滤波器。IDT线距为1.3 μm。所制备的声表面波滤波器带通频率为1.1 GHz，声表面波速度为5620 km/s。这些值与估计值的误差在1.8%以内（见文献(5)）。通过这些研究，我们获得了大量关于如何在p型金刚石上生长立方AlN的数据。少

The research subject we studied in the fiscal year 2000 was to evaluate the p-type diamond as the SAW substrate and the deposition method of a thin film AlN grown on the diamond. The conduction mechanism of the heavily doped p-type diamond was analyzed. The diamond is a semiconductor with a wide band gap energy of 5.5 eV, and has a different conduction mechanism from that of Si and GaAs having a band gap energy of about 1 eV.When the impurity concentration increases, a new and shallower impurity level is formed due to the interaction between the impurities, and the carriers moves via this level. This mechanism was demonstrated by the use of a sandwich structure of lightly doped p-type diamond in between the heavily doped p-type diamonds with impurity band conduction (see the references (1), (5) and (6)).As for the deposition method for the AlN, we investigated two methods, one was the deposition at the resonance point of the nitrogen electron cyclotron plasma and the other was the conv … More entional metal organic chemical vapor deposition (MOCVD). By the use of MOCVD, we got good quality AlN at the deposition temperature of 1150℃. By the use of the former method, we succeeded in growing good quality AlN at the temperature lower than 600℃. This method enabled us to grow high quality AlN on metal Al hetero-epitaxially. By the use of this method, we fabricated AlN SAW filters onto the Al inter-digital-transducer (IDT) and we got the quality factor of 3 million at the fabricated SAW filter. This high quality factor is understood to be due to the Lamb wave excitation in the AlN thin film of uniform thickness. This result was reported at the International Workshop of Nitride (IWN 2000) at Nagoya (see reference (2,3)).To evaluate our computer simulation of the SAW filter, we made several SAW filters by the use of AlN grown on sapphire C-plane and on R-plane. The line and space of IDT was 1.3 μm. The fabricated SAW filters had a band-pass frequency of 1.1 GHz and SAW velocity of 5,620 km/s. These values were within 1.8% error of the estimated values (see reference (5)). From these investigations, we obtained plenty of data on how to grow cubic AlN onto p-type diamond. Less