含硅量子點氮化硅薄膜的發(fā)光特性及載流子輸運機理研究
發(fā)布時間：2018-09-07 10:01
【摘要】：硅量子點由于其獨特的量子限域效應(yīng)特性在發(fā)光二極管和太陽能電池等領(lǐng)域具備巨大潛力。特別地,含硅量子點氮化硅薄膜由于其良好的光學(xué)特性,且制備方式與現(xiàn)行成熟的互補金屬氧化物半導(dǎo)體(CMOS)工藝相兼容等優(yōu)勢成為極具潛力的硅基光源候選材料之一。然而,截至目前,對于含硅量子點氮化硅薄膜發(fā)光機制的探討還未有定論,量子限域效應(yīng)(QCE)發(fā)光,帶尾態(tài)發(fā)光和界面態(tài)發(fā)光等多種機制被提出；硅量子點發(fā)光器件的載流子輸運與硅量子點密度、缺陷態(tài)分布等密切相關(guān),也需進行深入分析；此外,當(dāng)前硅量子點器件的發(fā)光效率依然很低,有待提高�；诖�,本文采用等離子體增強化學(xué)氣相沉積(PECVD)方式沉積氫化非晶氮化硅(a-SiNx:H)薄膜,經(jīng)退火工藝凝析出硅量子點；研究了硅量子點生長規(guī)律以及氮化硅薄膜的微結(jié)構(gòu)及光致發(fā)光(PL)性能；制備了硅量子點發(fā)光器件并探索了其電致發(fā)光(EL)來源及其載流子輸運機理。本文主要的研究結(jié)果如下：通過調(diào)控NH3/SiH4流量比制備了富硅程度不同的a-SiNx:H薄膜,獲得了優(yōu)化的晶硅量子點和非晶硅量子點制備工藝；分析了退火過程中氮化硅薄膜的微結(jié)構(gòu)演變及硅量子點的生長機理。研究發(fā)現(xiàn),退火處理導(dǎo)致薄膜內(nèi)Si-H和N-H鍵斷裂,H將逃逸出薄膜,且薄膜內(nèi)趨向于形成化學(xué)劑量比的氮化硅。依據(jù)Raman譜,薄膜的富硅程度決定了硅量子點的生長狀況。富硅含量過高時,將導(dǎo)致硅量子點接連生長；而當(dāng)薄膜富硅程度太低時,將無法生長硅量子點。UV-Vis吸收譜研究發(fā)現(xiàn),H的逃逸顯著地降低了薄膜的光學(xué)帶隙；硅量子點的長大與晶化也影響著其光學(xué)帶隙。引入325 nm和532 nm兩波長激光研究了薄膜退火前后的PL特性；探索了退火溫度、時間對于薄膜PL的影響；結(jié)合UV-Vis吸收譜闡明了氮化硅薄膜PL來源。對于1100℃退火后有晶硅量子點析出薄膜,在325 nm波長激發(fā)下,退火前后PL譜中均有～1.75 eV源于缺陷態(tài)的發(fā)光峰；未退火樣品主峰來源于非晶硅量子點QCE發(fā)光；經(jīng)1100℃退火后薄膜PL由晶硅量子點的QCE發(fā)光占據(jù)主導(dǎo)。然而,在532 nm波長激發(fā)下,缺陷態(tài)發(fā)光被掩蓋；800℃和950℃退火薄膜的PL來源于帶尾態(tài)發(fā)光；而未退火和1100℃退火樣品,其PL來源并未改變,且1100℃退火樣品展現(xiàn)激發(fā)波長尺寸選擇激發(fā)。對于1100℃退火后析出有非晶硅量子點氮化硅,其在325 nm波長激發(fā)下退火前后的PL來源于缺陷態(tài)發(fā)光和氮化硅本身固有的發(fā)光。在532 nm波長激發(fā)下,未退火及800℃和950℃退火樣品的PL均源自帶尾態(tài)發(fā)光；而1100℃處理后薄膜的PL由非晶硅量子點的QCE發(fā)光占據(jù)主導(dǎo)。設(shè)計制備了ITO/SRN (Si QDs)/p-Si/Al結(jié)構(gòu)發(fā)光器件,對EL譜高斯分峰并對比PL譜分析了EL來源；依據(jù)I-V數(shù)據(jù)進行各可能傳導(dǎo)機制擬合,獲得了發(fā)光器件在各工作區(qū)域的載流子輸運機理。研究發(fā)現(xiàn)載流子遂穿過程中出現(xiàn)擇優(yōu)路徑選擇,導(dǎo)致分散發(fā)光亮點的出現(xiàn)。對于含晶硅量子點氮化硅發(fā)光器件,其EL主要來源于缺陷態(tài),僅在含硅量子點密度較大器件EL譜中發(fā)現(xiàn)～1.58 eV的子峰,其來源于晶硅量子點的QCE發(fā)光。載流子輸運依賴于薄膜中富硅含量,F-N和TAT隧穿在載流子傳輸中均可能占據(jù)主導(dǎo)。而對于含非晶硅量子點氮化硅發(fā)光器件,其EL來源于非晶硅量子點的QCE發(fā)光；此外,基于F-N和SCLC隧穿機制的載流子輸運在場強為0.55～1.55MV/cm和場強大于1.55 MV/cm區(qū)域分別占據(jù)主導(dǎo)。制備了Si/SiNy和SiNx/SiNy兩種含硅量子點多層結(jié)構(gòu)發(fā)光器件,發(fā)現(xiàn)其EL和PL均位于～590 nm,來源于晶硅量子點的QCE發(fā)光,而載流子輸運分別由TAT遂穿和F-N遂穿占據(jù)主導(dǎo)。
[Abstract]:Silicon quantum dots (QDs) have great potential in the fields of photodiodes and solar cells due to their unique quantum confinement effects. In particular, silicon-containing QDs-based silicon nitride thin films have great potential due to their excellent optical properties and compatibility with the current mature complementary metal oxide semiconductor (CMOS) processes. However, up to now, there is no final conclusion about the mechanism of luminescence of silicon nitride thin films containing silicon quantum dots. Many mechanisms have been proposed, such as quantum confinement effect (QCE), tail state luminescence and interface state luminescence. In addition, the luminous efficiency of silicon quantum dot devices is still very low and needs to be improved. Silicon quantum dot luminescent devices were fabricated and their electroluminescent (EL) sources and carrier transport mechanisms were explored. The main results are as follows: A-SiNx:H thin films with different Si-rich degree were prepared by adjusting the NH3/SiH4 flow ratio, and the optimized silicon content was obtained. The microstructure evolution of silicon nitride films and the growth mechanism of silicon quantum dots during annealing were analyzed. It was found that the Si-H and N-H bonds in the films were broken by annealing treatment, and H would escape from the films and tend to form chemical dose ratio silicon nitride in the films. The growth of silicon quantum dots depends on the degree of silicon. When the content of silicon is too high, it will lead to the growth of silicon quantum dots. When the degree of silicon-rich film is too low, it will be unable to grow silicon quantum dots. The PL properties of the films before and after annealing were studied by introducing 325 nm and 532 nm laser. The influence of annealing temperature and time on the PL properties of the films was explored. The PL source of the silicon nitride films was elucidated by UV-Vis absorption spectra. For the films annealed at 1100 C, the PL spectra before and after annealing were ~1.75 eV excited at 325 nm. The main peak of the unannealed sample comes from the QCE luminescence of the amorphous silicon quantum dots, and the QCE luminescence of the silicon quantum dots dominates the PL film annealed at 1100 C. However, the defect luminescence is masked under 532 nm excitation, the PL of the films annealed at 800 C and 950 C comes from the band tail luminescence, while the PL film annealed at 1100 The PL source of the samples annealed at 1100 C has not changed, and the samples annealed at 1100 The PL of samples annealed at 0 C and 950 C originated from tail state luminescence, while the PL of films annealed at 1100 C was dominated by QCE luminescence of amorphous silicon quantum dots. Carrier transport mechanism in various working regions of light emitting devices is obtained. It is found that the selective path selection occurs during carrier tunneling, resulting in the appearance of dispersed luminescent spots. Carrier transport depends on the silicon-rich content in the film, and F-N and TAT tunneling may dominate the carrier transport. For silicon nitride light-emitting devices containing amorphous silicon quantum dots, the EL originates from the QCE luminescence of amorphous silicon quantum dots; furthermore, carrier transport based on the F-N and SCLC tunneling mechanism may be dominant. Transport dominates in the region of 0.55-1.55 MV/cm and 1.55 MV/cm, respectively. Si/SiNy and SiNx/SiNy multilayer luminescent devices are fabricated. The EL and PL of these devices are located in the range of 590 nm, which originate from QCE luminescence of crystal silicon quantum dots. Carrier transport is dominated by TAT tunneling and F-N tunneling, respectively.
【學(xué)位授予單位】：華中科技大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2016
【分類號】：TN304.2
，
本文編號：2227930
[Abstract]:Silicon quantum dots (QDs) have great potential in the fields of photodiodes and solar cells due to their unique quantum confinement effects. In particular, silicon-containing QDs-based silicon nitride thin films have great potential due to their excellent optical properties and compatibility with the current mature complementary metal oxide semiconductor (CMOS) processes. However, up to now, there is no final conclusion about the mechanism of luminescence of silicon nitride thin films containing silicon quantum dots. Many mechanisms have been proposed, such as quantum confinement effect (QCE), tail state luminescence and interface state luminescence. In addition, the luminous efficiency of silicon quantum dot devices is still very low and needs to be improved. Silicon quantum dot luminescent devices were fabricated and their electroluminescent (EL) sources and carrier transport mechanisms were explored. The main results are as follows: A-SiNx:H thin films with different Si-rich degree were prepared by adjusting the NH3/SiH4 flow ratio, and the optimized silicon content was obtained. The microstructure evolution of silicon nitride films and the growth mechanism of silicon quantum dots during annealing were analyzed. It was found that the Si-H and N-H bonds in the films were broken by annealing treatment, and H would escape from the films and tend to form chemical dose ratio silicon nitride in the films. The growth of silicon quantum dots depends on the degree of silicon. When the content of silicon is too high, it will lead to the growth of silicon quantum dots. When the degree of silicon-rich film is too low, it will be unable to grow silicon quantum dots. The PL properties of the films before and after annealing were studied by introducing 325 nm and 532 nm laser. The influence of annealing temperature and time on the PL properties of the films was explored. The PL source of the silicon nitride films was elucidated by UV-Vis absorption spectra. For the films annealed at 1100 C, the PL spectra before and after annealing were ~1.75 eV excited at 325 nm. The main peak of the unannealed sample comes from the QCE luminescence of the amorphous silicon quantum dots, and the QCE luminescence of the silicon quantum dots dominates the PL film annealed at 1100 C. However, the defect luminescence is masked under 532 nm excitation, the PL of the films annealed at 800 C and 950 C comes from the band tail luminescence, while the PL film annealed at 1100 The PL source of the samples annealed at 1100 C has not changed, and the samples annealed at 1100 The PL of samples annealed at 0 C and 950 C originated from tail state luminescence, while the PL of films annealed at 1100 C was dominated by QCE luminescence of amorphous silicon quantum dots. Carrier transport mechanism in various working regions of light emitting devices is obtained. It is found that the selective path selection occurs during carrier tunneling, resulting in the appearance of dispersed luminescent spots. Carrier transport depends on the silicon-rich content in the film, and F-N and TAT tunneling may dominate the carrier transport. For silicon nitride light-emitting devices containing amorphous silicon quantum dots, the EL originates from the QCE luminescence of amorphous silicon quantum dots; furthermore, carrier transport based on the F-N and SCLC tunneling mechanism may be dominant. Transport dominates in the region of 0.55-1.55 MV/cm and 1.55 MV/cm, respectively. Si/SiNy and SiNx/SiNy multilayer luminescent devices are fabricated. The EL and PL of these devices are located in the range of 590 nm, which originate from QCE luminescence of crystal silicon quantum dots. Carrier transport is dominated by TAT tunneling and F-N tunneling, respectively.
【學(xué)位授予單位】：華中科技大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2016
【分類號】：TN304.2
，
本文編號：2227930
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