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制作平面Gunn畴雪崩器件的材料是在掺Cr的高阻GaAs衬底上汽相外延一层n-GaAs,其电子浓度为1×10~(15)～1×10~(18)cm~(-3),厚度为6～15μm,迁移率为4000～7500cm~2/V·s。在这样的材料上生长SiO_2,常压下,当衬底温度大于630℃时,由于As的升华,使GaAs的晶体完整性受到损坏,而在较低温度下(如420～450℃)淀积时,SiO_2常出现破裂或脱落现象。 GaAs的热膨胀系数为5.9×10~(-6)℃~(-1),而SiO_2为0.4×10~(-6)℃~1,相差一个数量级以上;此外,SiO_2的应力,300K时为1～6×10~3N/cm。实验表明,在GaAs上淀积的SiO_2厚度超过5000(?)时便产生破裂。而P_2O_5在GaAs上淀积1500(?),却未观察到裂纹,因为P_2O_5的热
The material of the planar Gunn-type avalanche device is a layer of n-GaAs vapor-phase epitaxy on a Cr-doped high-resistance GaAs substrate with an electron concentration of 1 × 10 15 to 1 × 10 18 cm -3. 3) having a thickness of 6-15 μm and a mobility of 4000-7500 cm -2 / V · s. The growth of SiO 2 on such a material causes the crystalline integrity of GaAs to be impaired due to sublimation of As at atmospheric pressure at a substrate temperature of more than 630 ° C while being deposited at a relatively low temperature (e.g., 420 to 450 ° C) When, SiO_2 often rupture or shedding phenomenon. The thermal expansion coefficient of GaAs is 5.9 × 10 -6 C -1, while that of SiO 2 is 0.4 × 10 -6 C -1, which is more than one order of magnitude. In addition, the stress of SiO 2 is 1 at 300 K ~ 6 × 10 ~ 3N / cm. Experiments show that when the thickness of SiO 2 deposited on GaAs is over 5000 (?), Rupture occurs. However, P2O5 deposited on GaAs for 1500 (?), But no cracks were observed because of the heat of P2O5