Temperature dependence of electroluminescence of Er ions in tunnel diodes based on (111)Si:(Er,O)

Electroluminescence and current-voltage characteristics of tunnel diodes obtained by implantation of Er, O, and B ions into n-Si(111) with the subsequent heat treatment are investigated in a temperature range of 80–300 K in the breakdown mode. The observed increase in electroluminescence intensity with temperature for Er ions is caused by thermal emptying of the traps that captured the holes in the n-region of the diode at low temperatures. This emptying leads to a variation in the breakdown characteristics. It is shown that some of the traps at low temperatures retain the charge captured even after the voltage applied to the diode is switched off. This circumstance gives rise to the peculiar memory effect in the structures investigated.     

Influence of erbium ion implantation dose on characteristics of (111) Si:(Er, O) light-emitting diodes operating in p-n-junction breakdown mode

Characteristics of Si:(Er, O) light-emitting diodes (LEDs) fabricated by ion implantation on single-crystal (111) Si substrates and operating under the conditions of avalanche or tunneling breakdown of the p-n junction were studied. The Er³⁺ electroluminescence (EL) intensity depends nonmonotonically on the concentration of implanted rare-earth ions. An increase in the Er³⁺ ion EL intensity with temperature is observed in some tunneling diodes.     

Tunnel light-emitting Si:(Er,O) diodes with a short rise time of Er3+ electroluminescence under breakdown conditions

Si:(Er,O)-based tunnel light-emitting diodes were fabricated and exhibited the shortest ever recorded characteristic rise time for erbium electroluminescence. This is due to the formation of Er-related centers with an effective excitation cross section for erbium ions of ∼7×10⁻¹⁶ cm² and an excited-state lifetime of ∼17 μs. The lifetime of the first excited state of erbium ions after turning off the reverse current was measured for the first time; this lifetime is associated with Auger energy transfer to free electrons in the electrically neutral region of the diode. __________ Translated from Fizika i Tekhnika Poluprovodnikov, Vol. 34, No. 8, 2000, pp. 965–969. Original Russian Text Copyright ? 2000 by Emel’yanov, Sobolev, Trishenkov, Khakuashev.     

Nature of the edge electroluminescence peak in the Si:(Er,O) diode breakdown mode

Electroluminescence (EL) of erbium-and oxygen-doped Si:(Er,O) diodes at λ=1.00–1.65 μm has been studied in the p-n junction breakdown and forward current modes. The EL was measured at room temperature from the front and back surfaces of the diodes. A peak corresponding to the absorption band edge of silicon was observed in the EL spectra of some diodes in the p-n junction breakdown mode. The peak is associated with the injection of minority carriers from the metal contact into silicon, with subsequent band-to-band radiative recombination. The band-to-band recombination intensity increases sharply on reaching a certain current density that depends on the fabrication technology. This threshold current density decreases with the temperature of post-implantation annealing of Si:(Er,O) diodes increasing in the range 900–1100°C. __________ Translated from Fizika i Tekhnika Poluprovodnikov, Vol. 36, No. 4, 2002, pp. 453–456. Original Russian Text Copyright ? 2002 by Emel’yanov, Nikolaev, Sobolev.     

Effect of doping with nitrogen on electrical properties and erbium electroluminescence of a-Si:H(Er) films

The effect of nitrogen doping on the electrical and electroluminescence properties of amorphous hydrogenated silicon films doped with erbium has been studied. The parameters of the material, the characteristics of structures on its base, and the efficiency of Er electroluminescence (λ=1.54 μm) are determined by the excess of the nitrogen doping level over the background value depending on the Er concentration. It is shown that effectively luminescing structures can be obtained by reducing the background concentration, with nitrogen doping remaining at the level of ∼10²¹ cm⁻³. A possible mechanism is proposed, accounting for this effect in terms of two possible forms of nitrogen incorporation into an Er-doped a-Si:H structure: with either an Er-N complex or a Na ₄ ⁺ -Si ₃ ⁻ charged defect pair formed. In this case, the electroluminescence efficiency is determined by the number of these pairs. __________ Translated from Fizika i Tekhnika Poluprovodnikov, Vol. 35, No. 10, 2001, pp. 1250–1255. Original Russian Text Copyright ? 2001 by Kon’kov, Terukov, Granitsyna.     

Influence of the orientation of the silicon substrate on the properties of avalanche Si:Er:O light-emitting structures

The influence of the orientation of silicon on the structural and luminescence properties of avalanche light-emitting diodes fabricated by the coimplantation of erbium and oxygen followed by solid-phase epitaxial (SPE) crystallization of the amorphized layer is considered. The luminescence properties are a consequence of the formation of various structural defects during the SPE crystallization: V-shaped dislocations and erbium precipitates form in (100) Si:Er:O layers, and larger structural defects, i.e, twins, are observed in (111) Si:Er:O layers along with an increase in the dislocation density by more than four orders of magnitude in comparison with the (100) orientation. The luminescence properties of avalanche and tunnel light-emitting diodes are also compared. In contrast to tunnel diodes, in avalanche diodes erbium ions are excited in the entire space-charge layer, and the effective excitation cross section of the Er³⁺ ions and their lifetime in the excited state are 3–4 times larger. Fiz. Tekh. Poluprovodn. 33, 660–663 (June 1999)     

Effect of the annealing temperature on the low-temperature photoluminescence in Si:Er light-emitting structures grown by molecular-beam epitaxy

The photoluminescence spectra of light-emitting structures based on silicon doped with erbium during the course of molecular-beam epitaxy at a temperature of 500°C are studied at 4.2 K on being annealed at 800–900°C. Three sets of lines belonging to the emitting centers of erbium in silicon with a low oxygen-impurity concentration are revealed.     

Capacitance-voltage characteristics of p-n structures based on (111)Si doped with erbium and oxygen

Capacitance-voltage characteristics of tunneling diodes fabricated by co-implantation of erbium and oxygen in single-crystal (111)Si wafers have been studied. Anomalous enhancement of the p-n-junction capacitance with increasing reverse bias has been observed at certain temperatures depending on the implantation dose. The rise in capacitance (decrease in the space charge region width) is associated with the formation of deep levels of high density in the band gap of n-layer of the p-n junction and electron emission from these levels in the space charge region with increasing voltage. The obtained results show that the parameters of the defects responsible for the levels depend on the erbium and oxygen implantation doses.     

Effect of parameters of Ge(Si)/Si(001) self-assembled islands on their electroluminescence at room temperature

The electroluminescence (EL) of multilayered p-i-n structures with the self-assembled Ge(Si)/Si(001) islands are investigated. It is found that the structures with islands grown at 600°C have the highest intensity of the electroluminescence signal at room temperature in the wavelength range of 1.3–1.55 μm. The annealing of structures with the Ge(Si) islands leads to an increase in the EL-signal intensity at low temperatures and hampers the temperature stability of this signal, which is related to the additional Si diffusion into islands during annealing. The found considerable increase in the electroluminescence-signal intensity with the thickness of the separating Si layer is associated with a decrease in the elastic stresses in the structure with an increase in this layer’s thickness. The highest EL quantum efficiency in the wavelength range of 1.3–1.55 μm obtained in investigated structures amounted to 0.01% at room temperature.     

Ultrathin gate oxide CMOS on (111) surface-oriented Si substrate

The properties of ultrathin gate oxides in the direct-tunneling regime and the characteristics of the related CMOS transistors on a (111) surface-oriented Si substrate were investigated and compared with those on a (100) substrate for the first time. It was confirmed that low field mobility of n-MOSFETs on the (111) substrate is smaller than that on the (100) substrate and that of p-MOSFETs on (111) is larger than that on (100) until the direct-tunneling gate oxide regime. It has been found that most of the electrical properties of MOSFETs, with the notable exception of mobility, become almost identical for (100) and (111) substrates when the oxide thickness is reduced to less than 2.0 nm. Some of the properties are quite different between the two substrates for the thicker oxide case. It has been found that the reliability of hot carrier injection and time-dependent dielectric breakdown (TDDB) of the oxides and MOSFETs on the (111) substrate is slightly better than that on the (100) substrate. In addition, the characteristics and reliability of oxides and MOSFETs on a wafer tilted 4° from (100) axis were investigated. It was found that there are few differences in the mobility between (100) and (100) 4° off substrates for both n- and p-MOSFET cases. The reliability of oxides or MOSFETs on the wafer was identical to that on normal (100) substrate. These results suggest that ultrathin gate oxide MOSFETs on Si surfaces with various orientations are likely to have practical applications. This is good news for possible future new structures of MOSFETs such as vertical or three-dimensional (3-D) MOSFETs     

Features of impurity photoconductivity in Si:Er/Si epitaxial diodes

The photocurrent spectra of Si:Er/Si epitaxial diode structures are studied. It is shown that the nature of the sub-band-gap photoresponse is determined by the epitaxial growth temperature of the Si:Er layer and is not related to the composition of erbium emission centers. It is found that the absorption of light with photon energies lower than the energy-gap of silicon is determined by impurity-defect complexes that appear during the growth of the epitaxial layer and form a quasi-continuous spectrum of states in the energy gap of silicon. It is assumed that these impurity centers are not related to optically active erbium centers and are not involved in excitation-energy transfer to the rare-earth impurity.     

Blue electroluminescence in reverse-biased ZnS(Zn,Al) diodes

Diodes fabricated from ZnS crystals annealed in molten zinc containing 2% aluminium have been found to yield bright blue electroluminescence under reverse-bias at room temperature. Study of the electroluminescence and cathodoluminescence spectra for these diodes together with electron microprobe analysis and measurements of their current-voltage characteristics has led to an explanation of the blue electroluminescence excitation and emission mechanisms. The surface (～ 800 μm) of the ZnS(An,Al) crystal was found to be aluminium-rich. The aluminium provided additional donors to give a low-resistivity region. This region contained ZnAl₂S₄ phases in additional to the V_ZnAl complex defects that were thought to be responsible for the blue electroluminescence emission.     

Si(111)上生长LiNbO_3薄膜的研究

利用射频磁控溅射的方法,在Si(111)衬底上制备了LiNbO3薄膜。采用X射线衍射(XRD)和扫描电子显微镜(SEM)研究了衬底温度、退火温度和溅射气体压强对LiNbO3薄膜结晶和表面形貌的影响,并用椭圆偏振仪测量了薄膜的厚度和折射率。结果表明:衬底温度为450℃时制备的薄膜,退火前后都没有LiNbO3相生成;衬底温度为500～600℃时,LiNbO3薄膜出现(012)、(104)和(116)面衍射峰,经600℃退火后3个衍射峰的强度加强;衬底温度为600℃时,经600～900℃退火得到的LiNbO3薄膜,除出现(012)、(104)和(116)面衍射峰外,还出现(006)面衍射峰;溅射气体压强从0.8 Pa增大到2.4 Pa时,经800℃退火后得到的LiNbO3薄膜表面晶粒团簇变小,而0.8 Pa制备的薄膜经800℃退火后LiNbO3相的结晶程度较其它压强下完善;900℃退火后得到的LiNbO3薄膜折射率为2.25,与LiNbO3晶体相当。     

Specific features of the mechanisms of excitation of erbium photoluminescence in epitaxial Si:Er/Si structures

The excitation spectra and kinetics of erbium photoluminescence and silicon interband photoluminescence in Si:Er/Si structures under conditions of high-intensity pulse optical excitation are studied. It is shown that, in the interband photoluminescence spectra of the Si:Er/Si structures, both the luminescence of free excitons and the emission associated with the electron-hole plasma can be observed, depending on the excitation power and wavelength. It is found that the formation of a peak in the erbium photoluminescence excitation spectra at high pumping powers correlates with the Mott transition from the exciton gas to the electron-hole plasma. It is demonstrated that, in the Si:Er/Si structures, the characteristic rise times of erbium photoluminescence substantially depend on the concentration of charge carriers.     

Effect of silicon spacer thickness on the electroluminescence of multilayer structures with self-assembled Ge(Si)/Si(001) islands

The results of investigation of the electroluminescence of multilayer p-i-n structures with Ge(Si)/Si(001) self-assembled islands are presented. The nonmonotonic dependence of the room-temperature intensity of the electroluminescence signal from islands on the Si spacer thickness is revealed. The highest electroluminescence signal intensity is observed for structures with a Si spacer thickness of 15?C20 nm. The significant decrease detected in the electroluminescence signal from the islands in structures with thick Si spacers (>20 nm) is explained by the formation of defect regions in them. The observed decrease in the electroluminescence signal in structures with thin Si layers is associated with a decrease in the Ge fraction in the islands in these structures, which is caused by enhanced Si diffusion into islands with increasing elastic strains in the structure.     

Avalanche light-emitting diodes operating at room temperature based on single-crystal Si:Ho:O

Electroluminescence of Ho³⁺ ions has been observed for the first time in diode structures based on single-crystal silicon doped with holmium and oxygen. The product of the effective cross-section for excitation of Ho³⁺ ions and the lifetime of the first excited state was determined under avalanche breakdown conditions. Fiz. Tekh. Poluprovodn. 33, 931–932 (August 1999)     

AlGaN/GaN HEMTs on resistive Si(111) substrate grown by gas-sourceMBE

Al_0.3Ga_0.7N/GaN high electron mobility transistor (HEMT) structures have been grown on resistive Si(111) substrate by molecular beam epitaxy (MBE) using ammonia (NH₃). The use of an AlN/GaN intermediate layer allows a resistive buffer layer to be obtained. High sheet carrier density and high electron mobility arc obtained in the channel. A device with 0.5 μm gate length has been realised exhibiting a maximum extrinsic transconductance of 160 mS/mm and drain-source current exceeding 600 mA/mm. Small-signal measurements show f_t of 17 GHz and f_max of 40 GHz     

Growth of (111) HgCdTe on (100) Si by MOVPE using metalorganic tellurium adsorption and annealing

(lll)B CdTe layers free of antiphase domains and twins were directly grown on (100) Si 4°-misoriented toward<011> substrates, using a metalorganic tellurium (Te) adsorption and annealing technique. Direct growth of (lll)B CdTe on (100) Si has three major problems: the etching of Si by Te, antiphase domains, and twinning. Te adsorption at low temperature avoids the etching effect and annealing at a high temperature grows single domain CdTe layers. Te atoms on the Si surface are arranged in two stable positions, depending on annealing temperatures. We evaluated the characteristics of (lll)B CdTe and (lll)B HgCdTe layers. The full width at half maximum (FWHM) of the x-ray double crystal rocking curve (DCRC) showed 146 arc sec at the 8 |im thick CdTe layers. In Hg_1−xCd_xJe (x = 0.22 to 0.24) layers, the FWHMs of the DCRCs were 127 arc sec for a 7 (im thick layer and 119 arc sec for a 17 (im thick layer. The etch pit densities of the HgCdTe were 2.3 x 106 cm2 at 7 ^m and 1.5 x 106 cm-2 at 17 um.     

硅基高质量氧化锌外延薄膜的界面控制

本文利用反射式高能电子衍射(RHEED)、高分辨透射电镜和选区电子衍射方法,系统研究了Si(111)衬底上制备高质量氧化锌单晶薄膜的界面控制工艺.发现低温下Mg(0001)/Si(111)界面互扩散得到有效抑制,形成了高质量的单晶镁膜,进一步通过低温氧化法和分子束外延法实现了单晶MgO缓冲层的制备,从而为ZnO的外延生长提供了模板.在这一低温界面控制工艺中,Mg膜有效防止了Si表面的氧化,而MgO膜不仅为ZnO的成核与生长提供了优良的缓冲层,且极大地弛豫了由于衬底与ZnO之间的晶格失配所引起的应变.上述低温工艺也可用来控制其它活性金属膜与硅的界面,从而在硅衬底上获得高质量的氧化物模板.     

Light output improvement of GaN-based light-emitting diodes grown on Si (111) by a via-thin-film structure

This work reports the fabrication of via-thin-film light-emitting diode (via-TF-LED) to improve the light output power (LOP) of blue/white GaN-based LEDs grown on Si (111) substrates.The as-fabricated via-TF-LEDs were featured with a roughened n-GaN surface and the p-GaN surface bonded to a wafer carrier with a silver-based reflective electrode,together with an array of embedded n-type via pillar metal contact from the p-GaN surface etched through the multiple-quantum-wells (MQWs) into the n-GaN layer.When operated at 350 mA,the via-TF-LED gave an enhanced blue LOP by 7.8％ and over 3.5 times as compared to the vertical thin-film LED (TF-LED) and the conventional lateral structure LED (LS-LED).After covering with yellow phosphor that converts some blue photons into yellow light,the via-TF-LED emitted an enhanced white luminous flux by 13.5％ and over 5 times,as compared with the white TF-LED and the white LS-LED,respectively.The significant LOP improvement of the via-TF-LED was attributed to the elimination of light absorption by the Si (111) epitaxial substrate and the finger-like n-electrodes on the roughened emitting surface.