低溫GaN成核層MOCVD生長(zhǎng)工藝對(duì)GaN外延薄膜影響的研究
發(fā)布時(shí)間：2019-05-07 05:06
【摘要】：III族氮化物半導(dǎo)體材料的研究和應(yīng)用是目前半導(dǎo)體行業(yè)的熱點(diǎn)。GaN基半導(dǎo)體材料作為第三代半導(dǎo)體材料的代表，在高溫、高頻、微波、大功率光電子等領(lǐng)域得到了很大的發(fā)展，大量的研究也證明以GaN等為代表的寬禁帶、直接帶隙半導(dǎo)體材料仍有著廣闊的發(fā)展空間和發(fā)展前景。然而由于GaN熔點(diǎn)高，平衡蒸汽壓很大，GaN材料的制備極為困難并且成本極高，這也使得GaN的外延生長(zhǎng)主要在異質(zhì)襯底(如藍(lán)寶石)上進(jìn)行，但異質(zhì)襯底與GaN之間較大的晶格失配及熱失配導(dǎo)致后續(xù)生長(zhǎng)的GaN外延層具有很高的位錯(cuò)密度(約為108-1010cm2)，晶體質(zhì)量比較差。這些高密度的位錯(cuò)嚴(yán)重影響了半導(dǎo)體材料的晶體質(zhì)量和光電性能。為了提高GaN外延薄膜的生長(zhǎng)質(zhì)量，本文從成核層的生長(zhǎng)工藝入手，通過(guò)對(duì)成核層生長(zhǎng)時(shí)的溫度和氨氣流量?jī)蓚�(gè)工藝參數(shù)進(jìn)行優(yōu)化，提高了GaN外延薄膜的晶體質(zhì)量，并對(duì)成核層的生長(zhǎng)機(jī)理和對(duì)上層非摻雜GaN外延薄膜的影響機(jī)制作了進(jìn)一步的討論，其主要的研究成果如下： 首先，本文利用金屬有機(jī)化學(xué)氣相沉積(MOCVD)設(shè)備在藍(lán)寶石襯底上生長(zhǎng)了具有不同成核層生長(zhǎng)溫度(分別為610℃、630℃、650℃、670℃和690℃)的五組GaN外延薄膜樣品，并通過(guò)in-situ原位監(jiān)測(cè)以及AFM、HRXRD、PL和HALL等表征手段進(jìn)行檢測(cè)。結(jié)合實(shí)驗(yàn)數(shù)據(jù)可知，成核層的生長(zhǎng)溫度對(duì)GaN外延薄膜的晶體質(zhì)量有著重大的影響。只有在適合的溫度下，GaN成核層才會(huì)在退火后形成大小均一，密度適中的三維形核島，然后在后續(xù)的生長(zhǎng)過(guò)程中順利實(shí)現(xiàn)從3D生長(zhǎng)模式向2D生長(zhǎng)模式的轉(zhuǎn)變，最終得到高質(zhì)量的GaN外延薄膜。在成核層生長(zhǎng)溫度為650℃時(shí)，得到最為光滑致密的GaN外延薄膜，位錯(cuò)密度最低，光電性能最好，帶邊峰強(qiáng)度最高，，載流子濃度最低，載流子遷移率最高。 除溫度外，本文還探究了氨氣流量對(duì)低溫GaN成核層生長(zhǎng)過(guò)程的影響，以及對(duì)后續(xù)高溫非摻雜GaN外延薄膜晶體質(zhì)量的影響。本實(shí)驗(yàn)仍用Aixtron公司的MOCVD設(shè)備，采用兩步生長(zhǎng)法在藍(lán)寶石襯底上制備了成核層生長(zhǎng)時(shí)氨氣流量不同(分別為A樣品400sccm、B樣品800sccm、C樣品1200sccm、D樣品1600sccm、E樣品2400sccm)的五組GaN外延薄膜樣品。通過(guò)對(duì)實(shí)驗(yàn)所得的樣品進(jìn)行HRXRD、PL、AFM和HALL等測(cè)試得知，成核層生長(zhǎng)時(shí)的氨氣流量最優(yōu)值為800sccm，此時(shí)樣品刃型位錯(cuò)密度和螺型位錯(cuò)密度均為最低，并且具有最好的光電性能。
[Abstract]:The research and application of III nitride semiconductor materials is a hot spot in the semiconductor industry at present. Gan-based semiconductor materials, as the representative of the third generation semiconductor materials, have been greatly developed in the fields of high temperature, high frequency, microwave, high power photoelectron and so on. A large number of studies have also proved that direct band gap semiconductor materials with wide bandgap represented by GaN et al still have broad development space and prospect. However, due to the high melting point and high equilibrium vapor pressure of GaN, the preparation of GaN materials is very difficult and the cost is very high, which makes the epitaxial growth of GaN mainly on heterogeneous substrates (such as sapphire). However, the large lattice mismatch and thermal mismatch between heterogeneous substrate and GaN lead to high dislocation density (about 108-1010cm2) and poor crystal quality of GaN epitaxial layer. These high density dislocations seriously affect the crystal quality and photoelectric properties of semiconductor materials. In order to improve the growth quality of GaN epitaxial film, the crystal quality of GaN epitaxial thin film was improved by optimizing the temperature and ammonia flow rate during the growth of the nucleation layer from the point of view of the growth technology of the epitaxial layer, and the crystal quality of the epitaxial film was improved by optimizing the temperature and the flow rate of ammonia. The growth mechanism of the nucleation layer and the influence mechanism on the undoped GaN epitaxial film are discussed. The main results are as follows: firstly, the growth mechanism of the nucleation layer and the influence mechanism of the epitaxial film on the undoped layer are discussed. Five groups of GaN epitaxial films with different nucleation temperatures (610,630,650, 670 and 690 鈩
本文編號(hào)：2470796
[Abstract]:The research and application of III nitride semiconductor materials is a hot spot in the semiconductor industry at present. Gan-based semiconductor materials, as the representative of the third generation semiconductor materials, have been greatly developed in the fields of high temperature, high frequency, microwave, high power photoelectron and so on. A large number of studies have also proved that direct band gap semiconductor materials with wide bandgap represented by GaN et al still have broad development space and prospect. However, due to the high melting point and high equilibrium vapor pressure of GaN, the preparation of GaN materials is very difficult and the cost is very high, which makes the epitaxial growth of GaN mainly on heterogeneous substrates (such as sapphire). However, the large lattice mismatch and thermal mismatch between heterogeneous substrate and GaN lead to high dislocation density (about 108-1010cm2) and poor crystal quality of GaN epitaxial layer. These high density dislocations seriously affect the crystal quality and photoelectric properties of semiconductor materials. In order to improve the growth quality of GaN epitaxial film, the crystal quality of GaN epitaxial thin film was improved by optimizing the temperature and ammonia flow rate during the growth of the nucleation layer from the point of view of the growth technology of the epitaxial layer, and the crystal quality of the epitaxial film was improved by optimizing the temperature and the flow rate of ammonia. The growth mechanism of the nucleation layer and the influence mechanism on the undoped GaN epitaxial film are discussed. The main results are as follows: firstly, the growth mechanism of the nucleation layer and the influence mechanism of the epitaxial film on the undoped layer are discussed. Five groups of GaN epitaxial films with different nucleation temperatures (610,630,650, 670 and 690 鈩
本文編號(hào)：2470796
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