Si,S,Be,Mg离子注入GaAs白光快速退火特性研究

利用灯光瞬态退火处理Si,S离子注入SI-GaAs样品,在950℃5秒的条件下得到了最佳的电特性,Be,Mg离子注入SI-GaAs样品在800℃ 5秒退火得到了最佳的电特性.Si,S,Be注入GaAs样品在适当的条件下得到了陡峭的载流子剖面分布,而Mg注入的样品有Mg的外扩散和较大的尾部扩散.透射电镜测量表明,Si低剂量和Be大剂量注入退火后单晶恢复良好,而Si和Mg大剂量注入退火后产生了大量的二次缺陷.应用Si和Mg注入GaAs分别制作了性能良好的MESFET和β=1000的GaAIAs/GaA,双极型晶体管(HBT).     

Be~+注入GaAs掺杂

本文报道了在气体离子源中Be~+束流的引出,比较了Be~+注入GaAs的常规炉子热退火与红外快速退火行为,给出了Be~+注入GaAs和InGaAs形成的pn结特性。实验表明,用Be~+注入化合物半导体可作为制作器件的一种有效方法。     

High-transconductance p-channel AlGaAs/GaAs HFETs with low-energyberyllium and fluorine co-implantation self-alignment

The fabrication and electrical characteristics of p-channel AlGaAs/GaAs heterostructure FETs with self-aligned p⁺ source-drain regions formed by low-energy co-implantation of Be and F are reported. The devices utilize a sidewall-assisted refractory gate process and are fabricated on an undoped AlGaAs/GaAs heterostructure grown by MOVPE. Compared with Be implantation alone, the co-implantation of F⁺ at 8 keV with 2×10¹⁴ ions/cm² results in a 3× increase in the post-anneal Be concentration near the surface for a Be⁺ implantation at 15 keV with 4×10¹⁴ ions/cm². Co-implantation permits a low source resistance to be obtained with shallow p⁺ source-drain regions. Although short-channel effects must be further reduced at small gate lengths, the electrical characteristics are otherwise excellent and show a 77-K transconductance as high as 207 mS/mm for a 0.5-μm gate length     

Fabrication and characteristics of ion-implanted GaAs/GaAlAs integrated injection logic inverter

An integrated injection logic inverter has been realised in GaAs/GaAlAs material using ion implantation and Zn diffusion. Si ions have been implanted to merge the current source with the switching transistor, whereas the Be implantation provides the base contact. The shallow p+-emitter of the pnp current source has been fabricated by Zn diffusion. Instead of a lateral pnp transistor, which is typical in I2L technology, a vertical arrangement has been used. This type of transistor shows a better current efficiency and can be fabricated with a better uniformity in terms of base width. First results of an I2L inverter with a vertical pnp transistor are shown.     

半绝缘GaAs中Mg~++P~+双注入研究

本文对Mg~+和P~+双离子注入半绝缘GaAs的行为进行了研究.发现不论是常规热退火还是快速热退火,共P~+注入都能有效地提高注入Mg杂质的电激活率,其效果优于共As~+注入,共P~+注入的最佳条件是其剂量与Mg~+离子剂量相同,电化学C—V测量表明,双注入样品中空穴分布与理论计算值接近,而单注入样品中则发生严重偏离,快速热退火较常规热退火更有利于消除注入损伤.     

SI GaAS中S~+注入的电学特性

本文研究了经常规热退火和快速热退火后SIGaAs中S~+注入的电学特性.热退火后,GaAs中注入S~+的快扩散和再分布不决定于S~+或砷空位V_(AS)的扩散而决定于离子注入增强扩散.使用快速热退火方法能抑制注入S~+在GaAs中的增强扩散,明显减小S~+的再分布,可以获得适合于制造GaAs MESFET器件的薄有源层.     

Ion implantation effects on GaAs MESFETs

The effects of ion-implantation on the uniformity and the ultimately achievable performance of GaAs MESFETs are calculated. The results of an extensive study of the profiles of Si, Se, and Be ions implanted into GaAs are incorporated into a combined process and device model for GaAs MESFET technology. Taken into account are the scaling of transconductances with implantation energy, effects of implant profiles and impurities on low-gate-bias transconductances, dopant diffusion during annealing, effects of encapsulant thickness and etch depth on threshold-voltage uniformity, and effects of recoil atoms on threshold voltages for implants through Si₃N₄ and SiO₂ caps     

On the behaviour of buried oxygen implanted layers in highly doped GaAs

Highly doped GaAs substrate material (doping level 10¹⁸ cm⁻³) has been implanted with 350 keV O⁺ ions with doses of 10¹⁴ – 10¹⁶ cm⁻² to produce high resistivity layers which are stable at high temperatures. LPE growth of flat GaAs epilayers onto the implanted wafers was achieved up to doses of about 1 × 10¹⁵ O⁺/cm² and 5 × 10¹⁵O⁺/cm² for RT and 200°C implants, respectively. N-o-n and p-o-n structures (o: oxygen implanted) were fabricated in which breakdown voltages of up to 15 V were obtained. Examples for application of this isolation technique are shown.     

Annealing studies of Be-implanted GaAs0.6P0.4

Differential resistivity and Hall effect measurements and secondary ion mass spectrometry (SIMS) are used to study the annealing behavior of Be-implanted GaAs_0.6P_0.4. Results similar to that previously reported for Be-implanted GaAs are observed, including outdiffusion of Be into the Si₃N₄ encapsulant during 900‡C annealing of high dose implants. Nearly all (85–100%) of the Be remaining after a 900‡C, 1/2 hr anneal is electrically active. However, the electrical activation at low annealing temperatures (600–700‡C) is much lower in GaAs_0.6P_0.4 than in GaAs. A substantial amount of diffusion is observed even for the low fluence Be implants in GaAs_0.6P_0.4 annealed at 900‡C, indicating a greater dependence of the diffusion on defect-related effects in the ternary. This work was supported by the Joint Services Electronics Program (U.S. Army, U.S. Navy, U.S. Air Force) under Contract DAAB-07-72-C-0259, by Monsanto Company, and by the Naval Electronic Systems Command. On leave at Cornell University, Department of Electrical Engineering, Ithaca, NY 14853.     

Formation of heavily doped n-type layers in GaAs by multiple ion implantation

N-type layers in GaAs with high free electron concentrations have been produced by multiple implantation of Ga, As, or P with dopant species such as Se, Si, or Ge. The implants that have been investigated include Si, Si + P, Ge, Ge + As, Se, and Se + Ga. The multiple implants Si + P, Ge + As, and Se + Ga gave higher peak carrier concentrations, especially at lower anneal temperatures, than did the respective single implants Si, Ge, and Se. In fact, Ge when implanted alone produced a p-type layer while the Ge + As multiple implant produced an n-type layer. Multiple implants with Si and Ge as dopants showed significant thermal diffusion during the anneal. Multiple implants of Ga with Se, on the other hand, resulted in reduced thermal diffusion in comparison with single Se implants.     

Electron beam induced current imaging of near-contact regions insemi-insulating GaAs

Electron beam induced current (EBIC) in a scanning electron microscope has been used to image the internal electric field regions near implanted contacts on semi-insulating GaAs. Planar n⁺-i-p⁺ structures were fabricated with intercontact distances ranging from 5 to 100 μm. In cases where the diffusion length is short compared to the lengths of interest, the current collected is determined primarily by the local electric field profile. With no externally applied bias, we observe large current collection regions adjacent to the n⁺ contact, extending ~10-20 μm into the bulk material. Two-dimensional (2-D) imaging indicates that the regions are highly nonuniform. For small intercontact distances, the contact-related fields, which are produced by the diffusion and trapping of carriers from the contacts, can dominate the entire region. Changes in EBIC signal with the application of forward or reverse bias are used to monitor the interaction of the zero bias field and the applied field. This approach provides a good estimate of the field distributions in trap-dominated, high resistivity materials like semi-insulating GaAs, with a spatial resolution generally not obtained with other field imaging techniques     

Electrical properties of be-implanted GaA1-xPx

Hall effect and resistivity measurements on Be implanted GaAs_1-xP_x(x～0.38) indicate that essentially 100% doping efficiency may be obtained for normal Be concentrations after a 900°C anneal using either SiO₂ or Si₃N₄ as an encapsulant. The temperature dependence of hole mobility in these samples exhibits impurity banding effects similar to those reported in heavily Zn doped GaAs. Hall effect measurements in conjunction with successive thin layer removal techniques indicate there is no significant diffusion of the implanted Be during anneal for a fluence of 6×10¹³ ions/cm².     

Degradation of the doping profile of epitaxial GaAs layers due to an ion implantation process

In order to form an n+ layer on the top of n/n- epitaxial layers, Si+ was implanted into vapor epitaxial GaAs wafers. When the dopant of the epitaxial layer was sulfur, a significant doping profile degradation occurred at the interface of the n/n- epitaxial layers. A similar degradation was observed in Ar+-implanted sulfur-doped epitaxial layers. Degradation of the doping profile was quite small when silicon-doped epitaxial layers were used. These results can be explained by a radiation-enhanced diffusion of the doped sulfur in the epitaxial layer.     

Molecular beam deposition of low-resistance polycrystalline GaAs

Heavy doping of polycrystalline GaAs (poly-GaAs) with Be is investigated using low-temperature molecular beam deposition. A polycrystal grain size of 50-180 nm, which is appropriate for microfabrication, is obtained at a deposition temperature of 370-530°C. The resistivity of poly-GaAs decreases rapidly with increasing doping level NF_A, and it becomes in reverse ratio to N_A when N_A >2 x 10²⁰ cm^-3. Low deposition temperature and high As₄ pressure are also found to be effective in reducing resistivity. The minimum resistivity reported to date of 3.3 x 10^-3 Q-cm is achieved for Be-doped poly-GaAs with a grain size of 120 nm. These results show that the present poly-GaAs is very promising for applications to compound semiconductor devices.     

Material characterization of an ion-implantation process for p-type (InGa)As/GaAs quantum-well structures

We have performed a detailed study of the formation of Be⁺-implanted contacts to modulation-doped, p-channel, (InGa)As/GaAs, single-strained quantum wells. Photoluminescence at 4 K from these structures is shown to be an excellent monitor of implant and annealing effects, as corroborated by Hall-effect measurements. Rapid thermal annealing produced higher electrical activation of the Be implants than did arsine-over-pressure annealing at comparable temperatures, similar to the trend in bulk GaAs. In contrast to conventional, alloyed-contact technologies, the rapid-annealed, implanted structures provided ohmic contact to the quantum well even at 4 K.     

Improved GaAs power FET Performance using Be Co-implantation

Be co-implantation following the standard Si donor implantation improves the performance of directly implanted GaAs power FET's. The doping profile abruptness increases from 88 to 48 nm/decade. The device efficiency increases by at least 15 percent and the maximum output power by about 10 percent due to reduction in gate-drain breakdown current.     

Self-aligned GaAs MISFET's with a low-temperature-grown GaAs gateinsulator

GaAs MISFET's with a low-temperature-grown (LTG) GaAs gate insulator and ion-implanted self-aligned source and drain n⁺ regions are demonstrated. The resistivity and breakdown field of the LTG GaAs insulator were not changed appreciably by implantation and 800°C activation annealing. The gate leakage current remained very low at a value of approximately 1 μA per μm² of gate area at 3 V forward gate bias. Because of the reduced source and drain resistance, the drain saturation current and the transconductance of self-aligned MISFET's increased more than twofold after ion implantation     

Use of Au/Te/Ni films for ohmic contact to GaAs

Ohmic contacts to n-type GaAs are usually fabricated by alloying AuGe/Ni films on GaAs. Ge acts as a donor to GaAs for fabrication of the ohmic contact. In an attempt to replace Ge, which is an amphoteric impurity, with a group VI element to improve on the ohmic contact resistivity, experiments were done with AuTe and AuTe/Ni contacts. A very low resistivity of ∼5 × 10^-7Ω.cm²was obtained by alloying 1700 Å of AuTe film with 300 Å of nickel on top at 510°C. This is the lowest contact resistivity obtained with any material other than AuGe/Ni on n-type GaAs.     

Stress current behavior of InAlAs/InGaAs and AlGaAs/GaAs HBT's withpolyimide passivation

InAlAs/InGaAs and AlGaAs/GaAs HBTs, with heavily Be-doped base layers, have been fabricated and their reliability under excessive forward current tested. To understand the HBT material difference, a common process based on a polyimide planarization method is applied to the fabrication. While short-term degradation induced by stress current is observed for AlGaAs/GaAs HBTs, InAlAs/InGaAs HBTs are stable up to a current density of 1.5×10⁵ A/cm², indicating the absence of substantial Be diffusion. An analysis of base current has shown a striking contrast between the HBTs in terms of the stressing effect on the surface recombination along emitter junction periphery     

Long-term transient radiation-resistant GaAs FET's

The amplitude of long term, pulse-radiation-induced transients in ion implanted GaAs FET's has been reduced by up to two orders of magnitude by the addition of a deep buried p-layer beneath the active n-layer. The p-layer was formed by ion implantation of Be to depth of 0.8 µm below the Si implanted n-active channel. Backgating was also greatly reduced as indicated by a much smaller amplitude transient response following application of a positive gate pulse and by the absence of light sensitivity and looping in the current/ voltage (I-V) characteristics.