High-quality crystalline layer transfer from a silicon-on-insulator substrate onto a sapphire substrate using wafer bonding

We demonstrate layer transfer of 150 nm of Si from a 200-mm, silicon-on-insulator (SOI) substrate onto a sapphire substrate using low-temperature wafer bonding (T=150°C). The crystalline quality and the thermal stability of the transferred Si layer were characterized by x-ray diffraction (XRD). A broadening of the (004) Si peak is observed only for anneal temperatures T_A≥800°C, indicating some degradation of the crystalline quality of the transferred Si film above these temperatures. The measured electron Hall mobility in the bonded Si layer is comparable to bulk silicon for T_A≤800°C, indicating excellent material quality.     

Effect of growth conditions on incorporation of Si into Ga and As sublattices of GaAs during molecular-beam epitaxy

The effect of dopant concentration and growth-surface crystallographic orientation on the incorporation of Si into Ga and As sublattices was investigated during GaAs molecular-beam epitaxy. The epitaxial layers (epilayers) were grown on GaAs substrates with (100), 2°(100), 4°(100), and 8°(100) orientations at a temperature of 520°C and with (111)A, 2°(111)A, 2°(111)A, 5°(111)A, 6°(111)A, and 8°(111)A (where A = Ga) orientations at a temperature of 480°C. The Sidopant concentration was varied within 10¹⁷–10¹⁹ cm^?3. Through electrical and photoluminescent methods of investigation, the Si impurity was found to occur at the sites of both GaAs-layer sublattices not only as simple donors and acceptors (Si_Ga and Si_As), but also as Si_Ga-Si_As, Si_Ga-V_Ga, and Si_As-V_As complexes. The concentration of Si impurity in various forms depends on the doping level of the layers and on the growth-surface orientation. Amphoteric properties of Si manifest themselves more prominently on the (111)A face than on the (100) one. It is shown that impurity defects form at the stage of layer crystallization and depend on the growth-surface structure.     

High-resolution transmission electron microscopy of silicide formation and morphology development of Ni/Si and Ni/Si<Subscript>1−x</Subscript>Ge<Subscript>x</Subscript>

Nickel-silicide phase formation in the Ni/Si and Ni/Si_1−xGe_x (x=0.20) systems and its correlation with variations in sheet resistance have been studied using high-resolution transmission electron microscopy (HRTEM) and related techniques. Following a 500°C anneal, uniform and low-resistivity NiSi and NiSi_1−xGe_x (x<0.20) crystalline films were formed in the respective systems. Annealed at 900°C, NiSi₂, in the form of pyramidal or trapezoidal islands, is found to replace the NiSi in the Ni/Si system. After a 700°C anneal, threading dislocations were observed for the first time in the Ni/Si_1−xGe_x system to serve as heterogeneous nucleation sites for rapid lateral NiSi_1−xGe_x growth.     

Evidence of a thermally stable carbon-nitrogen deep level in carbon-doped,nitrogen-implanted,GaAs and AIGaAs

Nitrogen ion implantation is shown to form high resistivity regions (p_s ≥ 1 × 10¹⁰ Ω/) in C-doped GaAs and Al_0.35Ga_0.65As that remains compensated after a 900°C anneal. This is in contrast to oxygen or fluorine implantation in C-doped GaAs which both recover the initial conductivity after a sufficiently high temperature anneal (800°C for F and 900°C for O). In C-doped Al_0.35Ga_0.65As N- and O-implant isolation is thermally stable but F-implanted samples regain the initial conductivity after a 700°C anneal. A dose dependence is observed for the formation of thermally stable N-implant compensation for both the GaAs and AIGaAs samples. A C-N complex is suggested as the source of the compensating defect level for the N-implanted samples. Sheet resistance data vs anneal temperature and estimates of the depth of the defect levels are reported. This result will have application to heterojunction bipolar transistors and complementary heterostructure field effect transistor technologies that employ C-doped AIGaAs or GaAs layers along with high temperature post-implant isolation processing.     

Halogen lamp rapid thermal annealing of Si- and Be-implanted In0.53Ga0.47As

Halogen lamp rapid thermal annealing was used to activate 100 keV Si and 50 keV Be implants in In_0.53Ga_0.47As for doses ranging between 5 × 10¹²−4 × 10¹⁴ cm⁻². Anneals were performed at different temperatures and time durations. Close to one hundred percent activation was obtained for the 4.1 × 10¹³ cm⁻² Si-implant, using an 850° C/5 s anneal. Si in-diffusion was not observed for the rapid thermal annealing temperatures and times used in this study. For the 5 × 10¹³ cm⁻² Be-implant, a maximum activation of 56% was measured. Be-implant depth profiles matched closely with gaussian profiles predicted by LSS theory for the 800° C/5 s anneals. Peak carrier concentrations of 1.7 × 10¹⁹ and 4 × 10¹⁸ cm⁻³ were achieved for the 4 × 10¹⁴ cm⁻² Si and Be implants, respectively. For comparison, furnace anneals were also performed for all doses.     

Role of a Si0.95Ge0.05 epilayer cap on boron diffusion in silicon under inert and dry oxidizing ambient annealing

Silicon (Si) and Si with a 60 nm Si_0.95Ge_0.05 epilayer cap (Si_0.95Ge_0.05/Si) were implanted with 60 keV, 1×10¹³ cm⁻² boron (B) followed by annealing in nitrogen (N₂) or dry oxygen (O₂) in two different anneal conditions. B⁺implantation energy and dose were set such that the B peak is placed inside Si in Si_0.95Ge_0.05/Si samples and concentration independent B diffusion is achieved upon annealing. For samples annealed above 1075 °C, Ge diffusing from the Si_0.95Ge_0.05 epilayer cap in Si_0.95Ge_0.05/Si samples reached the B layer inside Si and resulted in retarded B diffusion compared to the Si samples. For annealing done at lower temperatures, diffusion of Ge from Si_0.95Ge_0.05 epilayer cap does not reach the B layer inside Si. Thus B diffusion profiles in the Si and Si_0.95Ge_0.05/Si samples appear to be similar. B diffusion in dry oxidizing ambient annealing of Si_0.95Ge_0.05/Si samples further depends on the nature of Si_0.95Ge_0.05 oxidation which is set by the duration and the thermal budget of the oxidizing anneal.     

Heterojunction diodes in 3C-SiC/Si system grown by reactive magnetron sputtering: Effects of growth temperature on diode rectification and breakdown

3C-SiC/Si heterojunction diodes were prepared by reactive magnetron sputtering of pure Si in CH₄-Ar discharge on Si(111) substrates kept at temperatures (T_s) ranging from 800 to 1000°C. A good diode rectification process started for films grown at T_s≤900°C. Heterojunction diodes grown at T_s = 850°C showed the best performance with a saturation current density of 2.4 × 10⁻⁴ A cm⁻². Diode reverse breakdown was obtained at a voltage of −110 V. The doping concentration (N_d) of the 3C-SiC films was calculated from 1/C² vs V plot to be 3 × 10¹⁵ cm⁻³. Band offset values obtained were −0.27 and 1.35 eV for the conduction and valence band, respectively. X-ray diffraction analysis revealed the film grown at T_s = 850°C to be single-phase 3C-SiC. The full width at half maximum of the 3C-SiC(111) peak was only 0.25 degree. Cross-sectional transmission electron microscopy showed the film to be highly (111)-oriented with an epitaxial columnar structure of double positioning domain boundaries.     

DEEP LEVEL DEFECTS IN SI-IMPLANTED LEC UNDOPED Si-GaAs

The residual electrically active defects in(4×10~(12)cm~(-2)(30KeV)+5×10~(12)cm~(-2)(130KeV))si-implanted LEC undoped si-GaAs activated by two-step rapid thermal annealing(RTA)LABELED AS 970℃(9S)+750℃(12S)have been investigated with deep level transient spec-troscopy(DLTS).Two electron traps ET_1(E_c-0.53eV,σ_n=2.3×10~(-16)cm~2)and ET_2(E_c-0.81eV,σ_n=9.7×10(-13)cm~2)are detected.Furthermore,the noticeable variations of trap's con-centration and energy level in the forbidden gap with the depth profile of defects induced by ion im-plantation and RTA process have also been observed.The[As_i·V_(As)·As_(Ga)]and[V_(As)·As_i·V_(Ga)·As_(Ga)]are proposed to be the possible atomic configurations of ET_1 and ET_2,respectively to explaintheir RTA behaviors.     

Nearly Perfect Electrical Activation Efficiencies from Silicon-Implanted Al<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>Ga<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript>N with High Aluminum Mole Fraction

Electrical activation studies of Al _x Ga_1−x N (x = 0.45 and 0.51) implanted with Si for n-type conductivity have been made as a function of ion dose and anneal temperature. Silicon ions were implanted at 200 keV with doses ranging from 1 × 10¹⁴ cm⁻² to 1 × 10¹⁵ cm⁻² at room temperature. The samples were subsequently annealed from 1150°C to 1350°C for 20 min in a nitrogen environment. Nearly 100% electrical activation efficiency was successfully obtained for the Si-implanted Al_0.45Ga_0.55N samples after annealing at 1350°C for doses of 1 × 10¹⁴ cm⁻² and 5 × 10¹⁴ cm⁻² and at 1200°C for a dose of 1 × 10¹⁵ cm⁻², and for the Al_0.51Ga_0.49N implanted with silicon doses of 1 × 10¹⁴ cm⁻² and 5 × 10¹⁴ cm⁻² after annealing at 1300°C. The highest room-temperature mobility obtained was 61 cm²/V s and 55 cm²/V s for the low-dose implanted Al_0.45Ga_0.55N and Al_0.51Ga_0.49N, respectively, after annealing at 1350°C for 20 min. These results show unprecedented activation efficiencies for Al _x Ga_1−x N with high Al mole fractions and provide suitable annealing conditions for Al _x Ga_1−x N-based device applications.     

Infrared studies of be-doped GaAs grown by molecular beam epitaxy at low temperatures

Samples of molecular beam epitaxial GaAs grown at low temperatures doped with Be defects are studied as a function of growth temperature (T_G)-by measuring their localized vibrational modes at 77K using BOMEM Fourier transform infrared spectrometer. Localized vibrational modes of⁹Be_Ga in samples grown at T_G>350°C have been identified at 482 cm⁻¹. Secondary ion mass spectroscopy measurements show that the densities of Be defects remain approximately constant as T_G is lowered, however, additional structure in the⁹Be_Ga localized vibrational mode is observed. Calculations based on Green's function theory suggest that the additional structure in Be-doped LT GaAs can best be explained in terms of a complex center [⁹Be_Ga-As_Ga] involving an intrinsic defect.     

ArF excimer laser-enhanced photochemical vapor deposition of epitaxial Si from Si2H6: A simple growth kinetic model

Photolysis of Si₂H₆ using 193 nm radiation from an ArF excimer laser has been used to deposit homoepitaxial Si films in the temperature range of 250 to 350°C. Photolytic decomposition of Si₂H₆ generates growth precursors which adsorb on to a hydrogenated Si surface. A growth kinetic model is proposed based on single-photon 193 nm absorption by Si₂H₆, and chemical reaction of the photofragments as they diffuse to the sub-strate surface. With the laser beam positioned parallel to the Si substrate, the deposi-tion yield of solid Si from photo-excited Si₂H₆ is estimated to be 0.20 ± 0.04. Growth rates vary linearly with laser intensity and Si₂H₆ partial pressure over a range of 1–15 mJ/cm² · pulse and 5–40 mTorr, respectively, and epitaxial films are deposited when laser intensity and Si₂H₆ partial pressure conditions are such that the initial photofragment concentration is less than ~10¹³ cm⁻³.     

Passivation of carbon acceptors during growth of carbon-doped GaAs,InGaAs, and HBTs by MOCVD

Carbon dopedp-type GaAs and In_0.53Ga_0.47As epitaxial layers have been grown by low-pressure metalorganic chemical vapor deposition using CC1₄ as the carbon source. Low-temperature post-growth annealing resulted in a significant increase in the hole concentration for both GaAs and In_0.53Ga_0.47As, especially at high doping levels. The most heavily doped GaAs sample had a hole concentration of 3.6 × 10²⁰ cm⁻³ after a 5 minute anneal at ≈400° C in N₂, while the hole concentration in In_0.53Ga_0.47As reached 1.6 × 10¹⁹ cm⁻³ after annealing. This annealing behavior is attributed to hydrogen passivation of carbon acceptors. Post-growth cool-down in an AsH₃/H₂ ambient was found to be the most important factor affecting the degree of passivation for single, uncapped GaAs layers. No evidence of passivation is observed in the base region of InGaP/GaAs HBTs grown at ≈625° C. The effect ofn-type cap layers and cool-down sequence on passivation of C-doped InGaAs grown at ≈525° C shows that hydrogen can come from AsH₃, PH₃, or H₂, and can be incorporated during growth and during the post-growth cool-down. In the case of InP/InGaAs HBTs, significant passivation was found to occur in the C-doped base region.     

Induced disorder of AlAs-AlGaAs-GaAs quantum-well heterostructures

The effects of induced disorder on the layered structure and luminescence properties of Al_xGa_1-xAs quantum-well heterostructures (QWH’s) grown at Ts = 750°C by metalorganic chemical vapor deposition (MO-CVD) are investigated. High-temperature thermal anneals in the range 1000–800°C > T_s result in the interdiffusion of Al and Ga and disordering of the QWH active region. Similar results are obtained at the much lower temperature 500–600°C < T₈ by impurity (Zn) diffusion, which greatly enhances the Al-Ga interdiffusion process. It is also possible, by the use of a Si₃N₄ surface mask, to disorder selectively only certain portions of a QWH, thus leaving unchanged the as-grown quantum-well layered structure in the remaining areas. Lower-bandgap QWH’s can be dis ordered and changed into higher-bandgap material, including from direct gap to indirect gap     

Influence of indium doping on the formation of silicon-(gallium vacancy) complexes in gallium arsenide grown by molecular-beam epitaxy at low temperatures

Low-temperature photoluminescence (PL) studies of gallium-arsenide layers grown by molecular-beam epitaxy at low (200 °C) temperatures (LT GaAs) and doped with silicon or a combination of silicon and indium have been performed. The PL spectra of as-grown samples reveal a shallow acceptor-based line only. After annealing, an additional line at ∼1.2 eV appears, which is attributable to Si_Ga-V _Ga complexes. The activation energy of complex formation is found to be close to the activation energy of migration of gallium vacancies and is equal to 1.9±0.3 eV for LT GaAs: Si. It is found that doping with a combination of silicon and indium leads to an increase in the activation energy of formation of Si_Ga-V _Ga complexes to 2.5±0.3 eV. We believe that this increase in the activation energy is controlled by the gallium vacancy-indium interaction through local lattice deformations. Fiz. Tekh. Poluprovodn. 33, 1187–1191 (October 1999)     

Electrical Activation Studies of Silicon-Implanted Al<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>Ga<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript>N with Aluminum Mole Fraction of 11% to 51%

Electrical activation studies of Si-implanted Al _x Ga_1−x N with an Al mole fraction of 11% to 51% have been carried out as a function of ion dose and annealing temperature. The Al _x Ga_1−x N samples were implanted at room temperature with Si ions at 200 keV in doses ranging from 1 × 10¹⁴ cm⁻² to 1 × 10¹⁵ cm⁻², and subsequently annealed from 1100°C to 1350°C for 20 min in a nitrogen environment. The maximum electrical activation efficiencies for the Al _x Ga_1−x N samples with an Al mole fraction less than 40% were obtained for samples implanted with the highest Si dose of 1 × 10¹⁵ cm⁻². On the other hand, for the Al _x Ga_1−x N samples with an Al mole fraction more than 40%, nearly perfect activation efficiencies of 99% and 100% were obtained for the samples implanted with the lowest Si dose of 1 × 10¹⁴ cm⁻². The mobility of the Si-implanted Al _x Ga_1−x N samples increased with increasing annealing temperature in spite of the increased number of ionized donors and thus increased impurity scattering, indicating that a greater amount of lattice damage is being repaired with each successive increase in annealing temperature. These results provide suitable annealing conditions for Si-implanted Al _x Ga_1−x N-based devices with an Al mole fraction from 11% to 51%.     

High C-doping of MOVPE grown thin AlxGa1−xAs layers for AlGaAs/GaAs interband tunneling devices

High hole concentrations in LP-MOVPE grown GaAs and AlGaAs layers can be achieved by intrinsic C-doping using TMGa and TMAl as carbon sources. Free carrier concentrations exceeding 10²⁰ cm⁻³ were realised at low growth temperatures between 520–540°C and V/III ratios <1.2. The C-concentration increases significantly with the Al-content in Al_xGa_1−xAs layers. We observed an increase in the atom- and free carrier concentration from 5·10¹⁹ cm⁻³ in GaAs to 1.5·10²⁰ cm⁻³ in Al_0.2Ga_0.8As for the same growth conditions. Interband tunneling devices with n-type Si and p-type C-doped AlGaAs layers and barriers made of Al_0.25Ga_0.26In_0.49P have been investigated.     

Effects of heat treatment on the 0.8 eV photoluminescence emission in GaAs grown by molecular beam epitaxy at low temperatures

We report 0.8 eV photoluminescence (PL) emission of GaAs grown at low temperatures between 325 and 400°C by molecular beam epitaxy. Effects of heat treatments of the 0.8 eV emission are compared with those of the 1.467 eV sharp bound exciton lines. This allows us to attribute the 0.8 eV emisson to the As-V_Ga center. We discuss the assigning of the As_i-V_Ga center to the well-known EL6. The PL intensity variation of 0.68 eV EL2 and 0.8 eV As_i-V_Ga seen in substrate materials is explained in terms of dislocation−mediated As_i-V_Ga transformation to EL2 whereas the PL intensity variation of 0.8 eV As_i-V_Ga for molecular beam epitaxy layers can be attributed to the growth condition.     

Distribution of hydrogen in silicon and silicon carbide following high-temperature proton irradiation

The distribution of hydrogen in Si and SiC following high-temperature proton irradiation (T _irr=20–700 °C) is studied by secondary-ion mass spectrometry. It is shown that the hydrogen concentration profile in SiC depends weakly on irradiation temperature. In Si appreciable alteration of the concentration profile is observed already at T _irr⋍300 °C, and the profile completely loses its concentration gradient at T _irr⋍700 °C. Fiz. Tekh. Poluprovodn. 33, 1409–1410 (December 1999)     

Interfacial reactions and electrical properties of Hf/p-Si0.85Ge0.15

Interfacial reactions and electrical properties of Hf/p-Si_0.85Ge_0.15 as a function of the annealing temperature were studied. Hf₃(Si_1−xGe)₂ and Hf(Si_1−xGe)₂ were initially formed at 500°C and 600°C, respectively. At temperatures above 400°C, Ge segregation out of the reacted layers associated with strain relaxation of the unreacted Si_0.85Ge_0.15 films appeared. At 780°C, agglomeration occurred in the Hf(Si_1−xGe_x)₂ films. All the as-deposited and annealed Hf/p-Si_0.85Ge_0.15 samples showed the formation of an ohmic contact. The lowest specific contact resistance around 10⁻⁵ ω cm² could be obtained for the Hf₃ (Si_1−xGe_x)₂ contacts to p-Si_0.85Ge_0.15 formed at 500°C. Below 500°C, the decrease of specific contact resistance with the annealing temperature is mainly caused by the formation of Hf₃(Si_1−xGe_x)₂ and an interfacial Ge-rich layer between the Hf₃(Si_1−xGe_x)₂ and unreacted Si_0.85Ge_0.15 films, while above 600°C, the increase of specific contact resistance may be due to the formation of Hf(Si_1−xGe_x)₂ and SiC as well as the roughness of the Hf(Si_1−xGe_x)₂ films.     

Effect of Si or Al interface layers on the properties of Ta and Mo contacts to p-type SiC

We present our results on the role of Si or Al interface layers on the structure and electrical properties of tantalum and molybdenum contacts to p-type 6H-SiC. Thin films of Ta or Mo were deposited on p-type SiC with and without p-doped Si or Al interface layers. The Ta/p-SiC, Ta/p-Si/p-SiC, Ta/Al/p-SiC, Mo/p-SiC, and Mo/Al/p-SiC structures were annealed at high temperatures up to 1200°C using the rapid thermal annealing process, in Ar-H₂ or N₂-H₂ ambient. X-ray diffraction analysis showed TaSi₂ in both Ta/p-SiC and Ta/p-Si/p-SiC structures annealed in Ar-H₂ ambient. For the N₂-H₂ ambient anneal tantalum nitride (TaN) was formed in Ta/p-SiC and Ta/Al/p-SiC, and TaN plus TaSi₂ in Ta/p-Si/p-SiC. While there was evidence of interaction between Mo and Si or Al no intermetallic phases were observed. Electrical measurements revealed that both TaN in Ta/p-SiC and TaN + TaSi₂ in Ta/p-Si/p-SiC structures made ohmic contacts, with specific contact resistances of about 2.13 × 10⁻³ and 1.47 × 10⁻¹ Ω-cm², respectively. The specific contact resistance for Ta/Al and Mo/Al layers on p-SiC decreases with increasing temperature and varies with anneal ambient. The values calculated for Ta/Al/p-SiC and Mo/Al/p-SiC were about 4.22 × 10⁻⁴ at 1100°C and 4.5 × 10⁻⁵ Ω-cm² at 1200°C, respectively. The heavy surface doping provided by Al in Ta/Al/p-SiC and Mo/Al/p-SiC is responsible for the low specific contact resistance.