Multiple-wavelength emission from In/sub x/Ga/sub 1-x/As-GaAs quantum wells grown on a nanoscale faceted GaAs substrate by molecular beam epitaxy

Multiple-wavelength photoluminescence (PL) spanning a 160-nm range from 980 to 1140 nm (77 K) has been obtained from In/sub x/Ga/sub 1-x/As-GaAs quantum wells (QWs) with varying In composition x on a nanoscale faceted (nanofaceted) GaAs substrate grown by molecular beam epitaxy. Five nanofaceted regions which consist of periodic [100]-(n11) (n = 3 or 1) facets along [011~] with different periods were prepared on a single substrate by interferometric lithography and selective growth of GaAs. The pattern period p was varied from infinity (large-area unpatterned) to 210 nm while the lateral width of the (n11) facet region was kept constant at /spl sim/180 to 200 nm within each period. A 5-nm-thick In/sub 0.23/Ga/sub 0.77/As layer was deposited on this multiple-period nanofaceted single GaAs surface in a single-run growth. Orientation-dependent migration and incorporation (ODMI) of In atoms [mass transport of incident In atoms from the (n11) to adjacent [100] facets] results in a variation of x of the In/sub x/Ga/sub 1-x/As layer section on the [100] facet as the width of the [100] facet was changed from /spl sim/20 to /spl sim/200 nm. ODMI induces a higher x on the [100] facet for smaller p. The PL exhibits a polarization dependence which is more pronounced for decreasing p [i.e., the width of [100] facet]. Consistent variations of the PL peak energy and linear polarization along the pattern direction confirm that ODMI results in a variation of the In composition and imply that the In/sub x/Ga/sub 1-x/As layer on a [100] facet has characteristics of a quantum wire as its width is decreased to /spl sim/20 nm for p = 210 nm. A possible application of nanopatterned growth to wavelength-division-multiplexing transmitters is discussed.     

High-saturation current wide-bandwidth photodetectors

This paper describes the design and performance of two wide-bandwidth photodiode structures. The partially depleted absorber photodiode utilizes an absorbing layer consisting of both depleted and undepleted In/sub 0.53/Ga/sub 0.47/As layers. These photodiodes have achieved saturation currents (bandwidths) of >430 mA (300 MHz) and 199 mA (1 GHz) for 100-/spl mu/m-diameter devices and 24 mA (48 GHz) for 100-/spl mu/m/sup 2/ area devices. Charge compensation has also been utilized in a similar, but modified In/sub 0.53/Ga/sub 0.47/As-InP unitraveling-carrier photodiode design to predistort the electric field in the depletion region in order to mitigate space charge effects. For 20-/spl mu/m-diameter photodiodes the large-signal 1-dB compression current and bandwidth were /spl sim/90 mA and 25 GHz, respectively.     

Multilayer (Al,Ga)N structures for solar-blind detection

We report on solar-blind metal-semiconductor-metal (MSM) detectors fabricated on stacks of (Al,Ga)N layers with different Al mole fraction. These structures were grown by molecular beam epitaxy on sapphire substrates to allow backside illumination and a low-temperature GaN buffer layer. They consist of a 0.3-0.4-/spl mu/m active layer grown on a thick (Al,Ga)N window layer (/spl ap/1 /spl mu/m) that is transparent at the wavelength of interest. Different Al contents were used in the window layer. We observed that, in general, samples with a high Al content were cracked, which is explained in terms of mechanical strain. MSM photodetectors fabricated on these samples showed large leakage currents that were correlated with the crack density. In order to reduce the strain and eliminate the cracks, we inserted an AlN layer between the buffer and window layer. A crack-free sample was obtained and the solar-blind photodetector fabricated on this structure showed record performance.     

High-power continuous-wave intracavity frequency-doubled Nd:GdVO/sub 4/-LBO laser under diode pumping into the emitting level

The continuous-wave high power laser emission of Nd:GdVO/sub 4/ at the fundamental wavelength of 1.06 /spl mu/m and its 531-nm second harmonic obtained by intracavity frequency doubling with an LBO nonlinear crystal is investigated under pumping by diode laser at 808 nm (on the /sup 4/I/sub 9/2//spl rarr//sup 4/F/sub 5/2/ transition) and 879 nm (on the /sup 4/I/sub 9/2//spl rarr//sup 4/F/sub 3/2/ transition). It is shown that, in spite of a lower absorption at 879 nm, the infrared emission is comparable under these two wavelengths of pump. The green emission performances were, however, improved by the 879 nm pump: 5.1 W at 531 nm with M/sup 2/=1.46 and 0.31 overall optical-to-optical efficiency was obtained from a 3-mm-thick 1-at.% Nd:GdVO/sub 4/ laser medium and a 10-mm-long LBO nonlinear crystal in a Z-type cavity for 16.5 W pump power. In similar conditions, the maximum green power for the 808 nm pump was 4.4 W, with 0.26 overall optical-to-optical efficiency and M/sup 2/=3.40 beam quality; at this pump wavelength the green emission shows evident saturation for pump power in excess of 9.9 W. This behavior is connected with the enhanced heat generation under 809-nm pumping, as evidenced by the increased thermal lensing of the fundamental emission. A careful alignment of the laser enables emission almost free of chaotic intensity fluctuations.     

UV laser diode with 350.9-nm-lasing wavelength grown by hetero-epitaxial-lateral overgrowth technology

We have demonstrated a UV-laser diode with a lasing wavelength of 350.9 nm, which has a GaN-AlGaN multiquantum-well (MQW) active layer and was grown on low-dislocation-density Al/sub 0.18/Ga/sub 0.82/N template. The Al/sub 0.18/Ga/sub 0.82/N template was produced by the hetero-epitaxial lateral overgrowth technology on the low-cost sapphire substrate, and has partially low-dislocation density of approximately 2/spl times/10/sup 7/ cm/sup -2/. The lasing operation under pulsed current injection was achieved with the threshold current density of 7.3 kA/cm/sup 2/ and the operating voltage of 10.4 V.     

Comparative study on the spectroscopic properties of Nd:GdVO/sub 4/ and Nd:YVO/sub 4/ with hybrid process

We have proposed a hybrid procedure for determining spectroscopic parameters for uniaxial solid-state laser crystals. Using our procedure, the spectroscopic properties of Nd:GdVO/sub 4/ were evaluated and compared to those of Nd:YVO/sub 4/. As a result, the peaks of absorption and stimulated emission cross sections of Nd:GdVO/sub 4/ in /spl pi/-polarization were determined to be 2.6 and 10.3/spl times/10/sup -19/ cm/sup 2/, respectively, and were smaller than those of Nd:YVO/sub 4/. On the other hand, the fluorescence lifetime of 1 at% Nd:GdVO/sub 4/ was evaluated to be 83.4 /spl mu/s, and was similar to 84.1 /spl mu/s of 1 at% Nd:YVO/sub 4/. Therefore, the product of stimulated emission cross section and fluorescence lifetime (/spl sigma//sub em//spl tau//sub f/ product) of Nd:GdVO/sub 4/ was smaller than that of Nd:YVO/sub 4/ under 1 at% of Nd/sup 3+/ doping concentration. The radiative lifetime of spontaneous emission of Nd:GdVO/sub 4/ was 168 /spl mu/s and was 1.9 times longer than that of Nd:YVO/sub 4/. Because of the low value of radiative quantum efficiency of Nd:GdVO/sub 4/ (50%), careful cavity design is required for creating a well performing solid-state laser with Nd:GdVO/sub 4/, based on the larger /spl sigma//sub em//spl tau//sub f/ product rather than the /spl sigma//sub em//spl tau//sub f/ product of Nd:YAG.     

Correlation between dielectric properties and sintering temperatures of polycrystalline CaCu/sub 3/Ti/sub 4/O/sub 12/

Dielectric properties of polycrystalline CaCu/sub 3/Ti/sub 4/O/sub 12/ (CCTO) pellets sintered in the temperature range 1000-1200/spl deg/C were evaluated with impedance spectroscopy at frequency range of 10/sup 2/ to 10/sup 7/ Hz from 90 K to 294 K. A correlation has been established between the pair values of low frequency limit dielectric constant and the total resistivity and the sintering temperature. For example, the sample sintered at 1100/spl deg/C demonstrates higher value of low frequency limit dielectric constant and lower value of total resistivity, while the sample sintered at 1000/spl deg/C demonstrates lower values of low frequency limit dielectric constant and higher value of total resistivity. This correlation has been successfully explained by relating with the difference in grain size and grain volume resistivities of these two polycrystalline CCTO samples. Further, it is suggested that donor doping of oxygen vacancies Vo' and Vo" may be the reason to cause the difference in the grain volume resistivities of these two samples.     

The impact of LOC structures on 670-nm (Al)GaInP high-power lasers

We investigate the potential of large optical cavity (LOC)-laser structures for AlGaInP high-power lasers. For that we study large series of broad area lasers with varying waveguide widths to obtain statistically relevant data. We study in detail I/sub th/, /spl alpha//sub i/, /spl eta//sub i/, and P/sub max/, and analyze above-threshold behavior including temperature stability and leakage current. We got as expected for LOC structures minimal /spl alpha//sub i//spl les/1 cm/sup -1/ resulting in /spl eta//sup d/=1.1 W/A for 64/spl times/2000 /spl mu/m/sup 2/ uncoated devices. We obtain total output powers /spl ges/3.2 W (qCW) and /spl ges/1.5 W (CW) at 20/spl deg/C.     

NO/sub x/ reduction after treatment system using nitrogen nonthermal plasma desorption

In the flue emission from an internal combustion system using diffusing combustion such as coal or oil fuel boiler, incinerator, or diesel engine, around 10% oxygen is usually included. It is difficult to reduce the NO/sub x/ in the emission completely using catalysts or plasma alone because part of the NO/sub x/ is oxidized under an O/sub 2/-rich environment. In order to overcome these difficulties, we proposed a new after treatment system of NO/sub x/ included in the exhaust gas of the combustion system using nonthermal plasma (NTP) desorption and reduction. In this system, exchangeable adsorbent columns are equipped. First, the exhaust gas including NO/sub x/ is adsorbed to an NO/sub x/ adsorbent for a period of /spl Delta/t/sub a/. After the period of /spl Delta/t/sub a/, the path of the exhaust gas is changed with a pair of rotary valves and NO/sub x/ adsorbent is changed. The adsorbed NO/sub x/ is desorbed from the adsorbent and reduced by applying NTP for a period of /spl Delta/t/sub d/ using N/sub 2/ or low-oxygen-concentration gas. The exhaust gas is always kept clean by the exchange of adsorbent. Further, total electric energy can be reduced because NTP is not applied for /spl Delta/t/sub a/. This system can be operated at atmospheric temperature because no catalyst is used. As an initial step to realize such kind of after treatment system, the basic characteristics of the N/sub 2/ NTP desorption and NO/sub x/ reduction were examined experimentally using a pulse corona NTP reactor. After several adsorption/desorption processes, the amount of NO/sub x/ adsorbed becomes equal to that of the NO/sub x/ desorbed, that is, all the NO/sub x/ was desorbed in a single desorption process. It is confirmed that the NO/sub x/ complete reduction using N/sub 2/ NTP desorption is possible not only for a simulated exhaust gas but for a real diesel engine gas. The effective specific energy density can be decreased down to 22 Wh/m/sup 3/.     

High-power scaling (>100 W) of a diode-pumped TEM/sub 00/ Nd:GdVO/sub 4/ laser system

We present results of an investigation to scale a diode-pumped A Nd:GdVO/sub 4/ laser system to high powers (>100 W) using a bounce amplifier configuration. A Nd:GdVO/sub 4/ laser oscillator with a bounce amplifier geometry, pumped by a single 40-W diode bar, gave 24 W of multimode output power (60% optical efficiency), and 20 W of TEM/sub 00/ output with M/sup 2/<1.05. Power scaling of the oscillator system with pumping by multiplexing two (nominally) 40-W diode bars gave 50.1 W of multimode output at 83-W diode pumping, 40 W of predominantly TEM/sub 00/ output from 81-W of diode pumping, and 34 W TEM/sub 00/ output (M/sup 2//sub x/=1.05,M/sup 2//sub y/=1.1) with an external slit spatial filter. Higher power scaling is achieved by using a master-oscillator power-amplifier (MOPA) configuration with the double-diode-pumped oscillator and a bounce amplifier pumped by a 3-bar diode stack. A multimode MOPA output of 100 W is achieved by single pass amplification with 145-W amplifier diode pumping and 104-W TEM/sub 00/ mode using a double bounce amplifier configuration with 180-W amplifier diode pumping.     

High-speed InSb photodetectors on GaAs for mid-IR applications

We report p-i-n type InSb-based high-speed photodetectors grown on GaAs substrate. Electrical and optical properties of photodetectors with active areas ranging from 7.06/spl times/10/sup -6/ cm/sup 2/ to 2.25/spl times/10/sup -4/ cm/sup 2/ measured at 77 K and room temperature. Detectors had high zero-bias differential resistances, and the differential resistance area product was 4.5 /spl Omega/ cm/sup 2/. At 77 K, spectral measurements yielded high responsivity between 3 and 5 /spl mu/m with the cutoff wavelength of 5.33 /spl mu/m. The maximum responsivity for 80-/spl mu/m diameter detectors was 1.00/spl times/10/sup 5/ V/W at 4.35 /spl mu/m while the detectivity was 3.41/spl times/10/sup 9/ cm Hz/sup 1/2//W. High-speed measurements were done at room temperature. An optical parametric oscillator was used to generate picosecond full-width at half-maximum pulses at 2.5 /spl mu/m with the pump at 780 nm. 30-/spl mu/m diameter photodetectors yielded 3-dB bandwidth of 8.5 GHz at 2.5 V bias.     

ITO-Schottky photodiodes for high-performance detection in the UV-IR spectrum

High-performance vertically illuminated Schottky photodiodes with indium-tin-oxide (ITO) Schottky layers were designed, fabricated, and tested. Ternary and quarternary III-V material systems (AlGaN-GaN, AlGaAs-GaAs, InAlGaAs-InP, and InGaAsP-InP) were utilized for detection in the ultraviolet (UV) (/spl lambda/<400 nm), near-IR (/spl lambda//spl sim/850 nm), and IR (/spl lambda//spl sim/1550 nm) spectrum. The material properties of thin ITO films were characterized. Using resonant-cavity-enhanced (RCE) detector structures, improved efficiency performance was achieved. Current-voltage, spectral responsivity, and high-speed measurements were carried out on the fabricated ITO-Schottky devices. The device performances obtained with different material systems are compared.     

Influence of doping concentration on the power performance of diode-pumped continuous-wave Tm/sup 3+/:YAlO/sub 3/ lasers

We investigated the effect of thulium ion concentration on the continuous-wave (CW) power performance of diode single-end-pumped thulium-doped YAlO/sub 3/ (Tm:YAP) lasers. Three samples with 1.5%, 3%, and 4% Tm/sup 3+/ concentration were examined at 18/spl deg/C. Lifetime and fluorescence measurements were further performed to assess the strength of cross relaxation and nonradiative decay. Our results showed that in single-end-pumped configurations, the best CW power performance was obtained with the 1.5% Tm:YAP sample, and laser performance of the samples degraded monotonically with increasing Tm/sup 3+/ concentration. By using 9.5 W of incident pump power at 797 nm, a maximum of 1430 mW of output power was obtained with the 1.5% Tm:YAP sample and 2% output coupler. We discuss how the effects of cross relaxation, reabsorption, nonradiative decay, and internal heating vary with increasing concentration. Spectroscopic measurements and rate-equation analysis suggest that cross relaxation should already be effective in samples with 1.5% Tm/sup 3+/ ion concentration and doping concentrations larger than 4% will lead to degradation in power performance due to higher nonradiative decay rates and larger reabsorption losses.     

High-power/high-brightness diode-pumped 1.9-/spl mu/m thulium and resonantly pumped 2.1-/spl mu/m holmium lasers

We report high power (>36 W) with beam propagation factor M/sup 2//spl sim/2 in a diode end-pumped Tm:LiYF/sub 4/ (Tm:YLF) laser generating output near the 1.91-/spl mu/m region. Using the 1.91-/spl mu/m emission and high brightness achieved with the Tm:YLF laser we resonantly end-pump the Holmium /sup 5/I/sub 7/ manifold in Ho:YAG and demonstrate /spl sim/19 W of continuous-wave (CW) output. The diode-to-Holmium optical to-optical conversion efficiency achieved is /spl sim/18%. Using a CW pumped and repetitively Q-switched configuration, the Tm:YLF pumped Ho:YAG laser achieves >16 W of output power with an M/sup 2//spl sim/1.48 at 15 kHz. A Q-switched frequency range of 9 to >50 kHz is also achieved.     

Nonselective wet oxidation of AlGaAs heterostructure waveguides through controlled addition of oxygen

We present data showing that the addition of trace amounts of O/sub 2/ (<1% relative to N/sub 2/) to N/sub 2/+H/sub 2/O process gas during the wet thermal oxidation of Al/sub x/Ga/sub 1-x/As enhances the oxidation rates of lower Al content (x /spl les/ 0.8) alloys (a tenfold increase for x=0.3), while decreasing the oxidation rate selectivity R(x=0.8)/R(x=0.3) by a factor of seven. An increase in the refractive index from 1.49 to 1.68, and a fourfold decrease in surface roughness, indicates the formation of a denser, higher quality oxide for x=0.3 AlGaAs. Oxides are characterized by prism coupling, atomic force microscopy, and scanning electron microscopy. Thermochemical calculations show a probable mechanism in the enhancement of the dry oxidation reactions of AlGaAs for low levels of O/sub 2/, while there is still an adequate quantity of H/sub 2/ produced to reduce As oxides in the wet oxidation process. An AlGaAs quantum well heterostructure p-n laser diode crystal is nonselectively oxidized to create a deep oxide, high-index contrast waveguide with potential applications in semiconductor photonic integrated circuits that require small bend radius, high isolation, low crosstalk optical waveguides.     

Thermal-stability improvement of a sulfur-passivated InGaP/InGaAs/GaAs HFET

The temperature-dependent characteristics of an InGaP/InGaAs/GaAs heterostructure field-effect transistor (HFET), using the (NH/sub 4/)/sub 2/S/sub x/ solution to form the InGaP surface passivation, are studied and demonstrated. The sulfur-passivated device shows significantly improved dc and RF performances over a wide temperature range (300-510 K). With a 1/spl times/100-/spl mu/m/sup 2/ gate-dimension HFET by (NH/sub 4/)/sub 2/S/sub x/ treatment, the considerably improved thermal stability over dc performances including lower temperature variation coefficients on the turn-on voltage (-1.23 mV/K), the gate-drain breakdown voltage (-0.05 mV/K), the gate leakage current (1.04 /spl mu/A/mm/spl middot/K), the threshold voltage (-1.139 mV/K), and the drain-saturation-current operating regimes (-3.11/spl times/10/sup -4//K) are obtained as the temperature is increased from 300 to 510 K. In addition, for RF characteristics, the sulfur-passivated device also shows a low degradation rate on drain-saturation-current operating regimes (-3.29/spl times/10/sup -4//K) as the temperature is increased from 300 to 400 K. These advantages provide the promise for high-speed high-frequency high-temperature electronics applications.     

Noise figure of parametric wavelength conversion with quasi-phase-matched LiNbO/sub 3/ waveguide

An analytical model of the noise accumulation in a chain of parametric wavelength converters is proposed. Signal-to-noise electrical power ratio is analytically given as a function of node number k in a chained transparent node system that consists of optical amplifiers, parametric wavelength converters, and several loss elements including optical transmission fiber with parameters of pump light excess noise /spl beta//sub p/, and average photon numbers per unit time of pump light and input signal , and , respectively, and spontaneous emission factor of optical amplifier n/sub sp/. The signal-to-noise degrades inversely proportional to node number k with the coefficient defined by NF/sup (1)/=2n/sub sp/+/spl beta//sub p// when k is lower than /Bo, where B/sub o/ represents optical bandwidth. The noise figure dependence on pump light quality /spl beta//sub p// and average photon number of input light in a single stage configuration are experimentally evaluated using Er-doped fiber amplifiers and quasi-phase-matched lithium niobate waveguide parametric wavelength conversion.     

Simultaneous removal of NO/sub x/, SO/sub x/, and CO/sub 2/ at elevated temperature using a plasma-chemical hybrid process

In previous studies, the authors confirmed that the plasma-chemical combined hybrid process for controlling NO flue gas emission was extremely effective and economical in comparison with the conventional selective catalytic reduction (SCR) system and other technologies. In the present study, we carried out experiments on the simultaneous removal of NO/sub x/ and SO/sub x/ at elevated temperature using the plasma-chemical hybrid process. A series of experiments was performed to quantify all the reaction byproducts such as N/sub 2/O, CO, HNO/sub 2/, HNO/sub 3/, NO/sub 3//sup -/, and SO/sub 4//sup -/ to evaluate the simultaneous NO/sub x/ and SO/sub x/ removal efficiency. The oxidation from NO to NO/sub 2/ without decreasing NO/sub x/ concentration (i.e., minimum reaction byproducts) and with least power consumption is the key for the optimum operation of the plasma reactor. The produced NO/sub 2/ was totally converted to N/sub 2/ and Na/sub 2/SO/sub 4/ with Na/sub 2/SO/sub 3/ or Na/sub 2/S with and without NaOH using the barrier-type packed-bed plasma reactor followed by the packed-column chemical reactor. The NO/sub 2/ reduction was more effective for Na/sub 2/S than Na/sub 2/SO/sub 3/ but produces H/sub 2/S with Na/sub 2/S. For both cases at least five times the stoichiometric amount of chemicals were required for complete NO/sub 2/ reduction. Nearly 100% of NO/sub x/ and SO /sub 2/ and 40% Of CO/sub 2/ simultaneous removal were achieved with less than 5 ppm of N/sub 2/O and CO. The operating cost was less than 1/4 the SCR process. The additional SO/sub 2/ treatment system can be eliminated.     

Dielectric and conductive spectra of the composite of barium titanate and LiClO/sub 4/-doped polyethylene oxide

Dielectric and conductive frequency spectra in a 10 mHz-10 GHz range have been measured for a composite consisting of barium titanate (BaTiO/sub 3/) inclusions dispersed in a LiClO/sub 4/-doped polyethylene oxide (Li-PEO) matrix with volume fraction /spl Phi/ = 0-40%. Pure Li-PEO behaves as a dielectric showing a segmental-mode dielectric relaxation at high frequencies (dielectric regime) and transfers to an ionic conductor below 10 MHz (conductive regime). BaTiO/sub 3/ is a ferroelectric having a very large dielectric permittivity and spontaneous polarization. The introduction of BaTiO/sub 3/ into Li-PEO caused a rapid increase in permittivity in the dielectric regime. In the conductive regime, the composite exhibited an additional relaxation at a frequency related to the ratio of DC conductivity of Li-PEO and the permittivity of BaTiO/sub 3/. This relaxation was attributed to accumulation of dissociated Li/sup +/ and ClO4/sup o/ns at the inclusion/matrix interface which resulted in an increase of effective permittivity and a decrease of effective conductivity. Quantitative analyses based on mixing laws for the two-phase spherical dispersion system have shown that the Bruggeman equation accurately predicted the /spl Phi/-dependence of the effective permittivity over the entire frequency range. Regarding the effective conductivity, it predicted values lower than the observed. We attributed this discrepancy to the spontaneous polarization of BaTiO/sub 3/, which induced ion trapping to reduce the DC conductivity of Li-PEO matrix.     

Numerical analysis of transmission coefficient,LDOS, and DOS in superlattice nanostructures of cubic $$\hbox {Al}_{x}\hbox {Ga}_{1-x}\hbox {N/GaN}$$ resonant tunneling MODFETs

Numerical analysis of the transmission coefficient, local density of states, and density of states in superlattice nanostructures of cubic \(\hbox {Al}_{x}\hbox {Ga}_{1-x}\hbox {N/GaN}\) resonant tunneling modulation-doped field-effect transistors (MODFETs) using \(\hbox {next}{} \mathbf{nano}^{3}\) software and the contact block reduction method is presented. This method is a variant of non-equilibrium Green’s function formalism, which has been integrated into the \(\hbox {next}\mathbf{nano}^{3}\) software package. Using this formalism in order to model any quantum devices and estimate their charge profiles by computing transmission coefficient, local density of states (LDOS) and density of states (DOS). This formalism can also be used to describe the quantum transport limit in ballistic devices very efficiently. In particular, we investigated the influences of the aluminum mole fraction and the thickness and width of the cubic \(\hbox {Al}_{x}\hbox {Ga}_{1-x}\hbox {N}\) on the transmission coefficient. The results of this work show that, for narrow width of 5 nm and low Al mole fraction of \(x = 20\,\%\) of barrier layers, cubic \(\hbox {Al}_{x}\hbox {Ga}_{1-x}\hbox {N/GaN}\) superlattice nanostructures with very high density of states of 407 \(\hbox {eV}^{-1}\) at the resonance energy are preferred to achieve the maximum transmission coefficient. We also calculated the local density of states of superlattice nanostructures of cubic \(\hbox {Al}_{x}\hbox {Ga}_{1-x}\hbox {N/GaN}\) to resolve the apparent contradiction between the structure and manufacturability of new-generation resonant tunneling MODFET devices for terahertz and high-power applications.