Millimeter Wave Reflection Data for Semi-Insulating Gallium Nitride on Sapphire Wafer

In order to estimate the dielectric properties of materials, we need vector measurements consisting of voltage reflection and transmission of electromagnetic radiation for the material under test (amplitude and phase). A recently developed apparatus for measuring time-resolved charge carrier dynamics in photo-responsive materials for millimeter-wave probe frequencies (TR-mmWC) was used to study dc reflection (amplitude only) characteristics of binary III/V direct bandgap material Gallium Nitride (GaN). Commercial-grade 2" N-GaN (Si-doped, high resistivity) on Sapphire wafer with thickness 430 +/- 25 micrometer and GaN layer thickness of 5 micrometers was used to collect reflected RF data using a Schottky barrier diode detector operable in the 110-170 GHz (D-waveguide band) range with responsivity around 2000 volts/watt. Output voltages of this negative polarity detector were collected in steps of 0.01 GHz. Reference voltages (E0) for reflection were collected by using a highly polished mirror. These data can be used to calculate the reflection coefficient (σ) of semi-insulating GaN. Anomalies in reflected voltages were observed in certain frequencies which may be neglected for this type of analysis. These frequencies to be flagged in the dataset are 110.4 GHz, 110.5GHz, 110.7GHz, 114.2 GHz, 114.7GHz, 114.8 GHz, 114.9GHz, 115GHz, 115.2GHz, 115.4GHz, 118.3GHz, 118.7GHz, and 156.4GHz. The cause of these anomalies could be the creation of standing wave/diffraction effects. Data were collected using Keithley digital multimeter operated with LabVIEW, 500 ms sampling period was used and a 30-sample average and standard deviation of signal voltages were stored in an ASCII-delimited comma-separated variable (.csv) file. Data column 1 is probe frequency, column2 is mirror reflected voltage, column 3 is the standard deviation of mirror reflected voltages. Column 4 is the GaN surface reflected voltage obtained at 65.4 degrees and column 5 is the standard deviation of GaN reflected voltage.

为估算材料的介电特性，需获取针对被测材料的电压反射与透射矢量测量数据（包含幅度与相位信息）。本研究采用一款新近研发的、用于毫米波探针频率下光响应材料载流子动力学时间分辨测量的测试装置（TR-mmWC），以研究二元III/V族直接带隙材料氮化镓（Gallium Nitride, GaN）的直流反射（仅幅度）特性。
实验使用商用级2英寸蓝宝石衬底上的N型氮化镓（硅掺杂、高电阻率）样品，衬底厚度为430±25微米，氮化镓层厚度为5微米；测试采用工作于110-170 GHz（D波导频段）范围的肖特基势垒二极管探测器（Schottky barrier diode detector），其响应度约为2000 V/W，用于采集反射射频（RF）数据。该负极性探测器的输出电压以0.01 GHz为步进进行采集。
反射参考电压（E0）通过高抛光镜面采集。本数据集可用于计算半绝缘氮化镓的反射系数（σ）。
研究中在部分频率下观测到反射电压异常，此类异常在本分析中可予以忽略。本数据集需标记的异常频率包括：110.4 GHz、110.5 GHz、110.7 GHz、114.2 GHz、114.7 GHz、114.8 GHz、114.9 GHz、115 GHz、115.2 GHz、115.4 GHz、118.3 GHz、118.7 GHz以及156.4 GHz。此类异常的成因可能为驻波/衍射效应的产生。
数据采集使用Keithley数字万用表配合LabVIEW软件完成，采样周期设为500 ms，同时将30次采样的信号电压平均值与标准偏差存储于ASCII分隔的逗号分隔变量（.csv）文件中。
数据各列含义如下：第1列为探针频率，第2列为镜面反射电压，第3列为镜面反射电压的标准偏差；第4列为65.4°入射角下测得的氮化镓表面反射电压，第5列为氮化镓反射电压的标准偏差。