A vertical porous InP structure with an aspect ratio larger than 100 was obtained by electrochemical anodization of a <111>A-oriented n-InP substrate with HCl etchant. The photoluminescence spectrum of this porous InP showed less surface recombination as well as a slight blue shift attributed to the quantum-size effect. By initiating the etching through SiO2-defined mask windows, which were prepared by electron-beam direct writing along 3 crystalline directions, a uniformly sized (around 72% within the permissible fluctuation error of about 4 nm against 100-nm-sized triangles), high-density (around 50%) structure was fabricated for the first time. These results reveal that this process is very attractive for the fabrication of high-density and low-size-fluctuation quantum-wire and -box structures.

Direct intensity modulation and wireless data transmission characteristics of terahertz-oscillating resonant tunnelling diodes (RTDs) is reported. A direct intensity modulation of the RTD oscillators was demonstrated, and the frequency response was measured. It was found that the 3 dB cutoff modulation frequency was limited by the parasitic elements of the external circuit, and increased up to 4.5 GHz by reducing such parasitic elements. Wireless data transmission by direct amplitude shift keying was demonstrated using an RTD oscillating at 542 GHz with cutoff frequency of 1.1 GHz. The BERs for bit rates of 2 and 3 Gbit/s were found to be 2 × 10 28 and 3 × 10 25 , respectively.Introduction: High-capacity short-distance wireless communication is an important application of the terahertz (THz) range [1, 2]. Thus, compact and coherent solid-state THz sources that can be modulated directly are highly desirable. A good candidate for THz sources is the resonant tunnelling diode (RTD), which can oscillate in the THz range at room temperature [3][4][5][6]. We have reported RTDs with fundamental oscillation of 1.04 THz [4] and high output power ( 400 mW) oscillation at around 550 GHz [5]. The modulation of the output of THz sources is important for communication. In this Letter, we demonstrate a direct modulation of the output power of an RTD oscillator and measure its frequency response. In addition, we also demonstrate wireless data transmission by a direct amplitude shift keying (ASK) of the RTD.

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Measurements are presented of the temperature dependence of the differential quantum efficiency ηd and threshold current density Jth of 1.6 µm In1-xGaxAsyP1-y lasers. The observed sharp decrease in ηd near room temperature is interpreted as due to absorption associated with transitions of electrons from the split-off valence band into holes injected into and thermally generated within the heavy hole valence band. Preliminary calculations using conventional laser theory predict a temperature variation corresponding to T0≃145 K. This together with the influence of ηd, appears to be sufficient to explain most of the observed temperature variation of Jth.

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