本文選題：氮化鎵　切入點：紫外探測器　出處：《江南大學(xué)》2017年碩士論文

【摘要】：作為第三代寬禁帶半導(dǎo)體材料的代表,氮化鎵(GaN)具有直接帶隙、光吸收系數(shù)大、抗輻射及耐高溫等優(yōu)良的材料特性,非常適合制備高性能的紫外探測器。這些探測器在導(dǎo)彈飛機預(yù)警、燃燒過程檢測、工業(yè)火焰探測以及環(huán)境紫外線檢測等領(lǐng)域都有重要的應(yīng)用價值。由于價格競爭優(yōu)勢,大多數(shù)GaN基紫外探測器制備在藍寶石襯底上,然而標準藍寶石襯底與GaN外延材料之間存在較大的晶格熱失配,薄膜內(nèi)部往往有較大的位錯密度,容易導(dǎo)致較大的反向漏電流密度,增加器件的背景噪音并降低光電轉(zhuǎn)化效率。目前,兩種有效改善GaN晶體質(zhì)量的方法是在圖形化藍寶石襯底(patterned sapphire substrate,PSS)上生長外延層,或者在生長外延層之前先生長緩沖層減小應(yīng)力。鑒于此,本論文主要在具有PSS和緩沖層襯底的外延片上制備了GaN基紫外探測器,具體的研究內(nèi)容歸納如下。1、搭建了相關(guān)的電學(xué)和光學(xué)特性測試系統(tǒng)。設(shè)計和搭建了高靈敏度的光電流瞬態(tài)響應(yīng)測試系統(tǒng),該系統(tǒng)具有極小的自響應(yīng)時間,約為8μs;設(shè)計和搭建了低頻噪聲測試系統(tǒng),能夠?qū)崿F(xiàn)對低頻1/f噪聲的精確測量;此外,從增強光源功率和減小光傳輸衰減兩個方面入手,優(yōu)化了光譜響應(yīng)測試系統(tǒng)。2、在基于PSS且摻雜漸變的GaN外延片上制備了肖特基型紫外探測器。與傳統(tǒng)結(jié)構(gòu)的器件相比,該器件表現(xiàn)出了顯著改善的電學(xué)和光學(xué)特性:室溫下,當偏壓為-5 V時,器件具有極低的暗電流密度~1.3×10~(-8) A/cm~2,在正向低偏壓下,隨著溫度的升高,電流輸運機制由隧穿為主變?yōu)閿U散與復(fù)合電流共同作用;在零偏壓下,紫外/可見光抑制比為~4.2×10~3,最高的響應(yīng)度為~0.147 A/W,最大外量子效率為~50.7%,甚至在深紫外波段(360 nm-250 nm)平均量子效率也大于40%;開啟時間和關(guān)閉時間約為~115μs和~120μs,基本不隨偏壓變化,且具有很好的熱穩(wěn)定性;零偏壓下熱噪聲限制的極限探測率為~5.5×10~(13) cm·Hz~(1/2)/W,-5 V偏壓時探測率約為~6.72×10~(10) cm×Hz~(1/2),同已報道的相似結(jié)構(gòu)器件的最高探測率處于同一個水平。3、制備了AlGaN基金屬-半導(dǎo)體-金屬型紫外探測器。通過在傳統(tǒng)藍寶石襯底和AlGaN外延層之間高溫生長AlN作為緩沖層來提高晶體質(zhì)量。結(jié)果表明:器件具有極低的暗電流~8 pA;在10 V電壓下的響應(yīng)度約為~0.07A/W,量子效率為~41.5%;器件的平均開啟時間和關(guān)閉時間約為~111μs和~77μs;熱噪聲限制的極限探測率為~4.89×10~(12) cm·Hz~(1/2)/W,-5 V偏壓時,器件探測率約為~6.26×10~9 cm×Hz~(1/2)。同時,還對器件進行了電壓應(yīng)力退化實驗,發(fā)現(xiàn)暗電流及響應(yīng)度隨應(yīng)力時間逐漸減小,但靜置一段時間后,光電參數(shù)又可恢復(fù)至受應(yīng)力前水平,推測可能是材料內(nèi)部的陷阱效應(yīng)所導(dǎo)致。
[Abstract]:As the representative of the third generation wide band gap semiconductor materials, gallium nitride (gan) has many excellent properties, such as direct band gap, large optical absorption coefficient, radiation resistance and high temperature resistance. Very suitable for the preparation of high performance UV detectors. These detectors have important applications in missile aircraft early warning, combustion process detection, industrial flame detection and environmental ultraviolet detection. Most GaN based UV detectors are fabricated on sapphire substrates. However, there is a large lattice thermal mismatch between standard sapphire substrates and GaN epitaxial materials. At present, two effective methods to improve the quality of GaN crystals are to grow epitaxial layers on patterned sapphire substrates on graphical sapphire substrates. Or the buffer layer is grown to reduce the stress before the epitaxial layer is grown. In view of this, the GaN based UV detector is prepared on the epitaxial wafer with PSS and buffer substrate. The specific research contents are summarized as follows: 1. A related electrical and optical characteristic testing system is built. A high sensitivity photocurrent transient response test system is designed and built. The system has minimal self-response time. It is about 8 渭 s. The low frequency noise measurement system is designed and built, which can accurately measure the low frequency 1 / f noise. In addition, it starts from two aspects: enhancing the power of light source and reducing the attenuation of optical transmission. Schottky type UV detector was fabricated on the GaN epitaxial wafer based on PSS and doped with gradient. Compared with the traditional device, the device showed significantly improved electrical and optical properties: at room temperature, the optical and electrical properties of the device were improved. When the bias voltage is -5 V, the device has a very low dark current density of 1.3 脳 10 ~ (-8) A / cm ~ (-2). At the positive low bias voltage, the current transport mechanism changes from tunneling to diffusion and composite current with increasing temperature, and at zero bias voltage, The UV / VIS ratio is 4.2 脳 10 ~ (-3), the highest responsivity is 0.147 A / W, and the maximum external quantum efficiency is 50.7, even in the deep ultraviolet band, the average quantum efficiency is more than 400.The opening time and closing time are about 115 渭 s and 120 渭 s, which basically do not change with bias voltage. And has good thermal stability; The limit detectivity of thermal noise limit under zero bias voltage is 5.5 脳 10 ~ (10) ~ (13) cm ~ (-1 / 2) / W ~ (-5) V bias. The detection rate is about 6.72 脳 10 ~ (10) ~ (10) cm 脳 10 ~ (10) cm ~ (-1) ~ (2) ~ (-1) ~ (-1) ~ 2 ~ (-1), which is at the same level as the reported maximum detectivity of similar structure devices. The AlGaN based metal-semiconductor-metal violet has been prepared. External detectors. The crystal quality is improved by growing AlN as a buffer layer between the traditional sapphire substrate and the AlGaN epitaxial layer. The results show that the device has a very low dark current of 8 Pa, and the responsivity is about 0.07 A / W at 10 V voltage. The quantum efficiency is 41.5; the average opening time and closing time are about 111 渭 s and 77 渭 s; the limit detectivity of thermal noise limit is 4.89 脳 10 ~ (-1) cm ~ (-1 / 2) / W ~ (-5) V bias voltage. The detection rate of the device is about 6.26 脳 10 ~ 9 cm 脳 Hz ~ (-1 / 2). At the same time, the voltage stress degradation experiments are carried out. It is found that the dark current and the responsivity decrease gradually with the stress time, but after a period of time, the optoelectronic parameters can be restored to the pre-stress level. It is speculated that the trap effect inside the material may be the result.
【學(xué)位授予單位】：江南大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TN23

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