Electron irradiation effects in polyimide passivated InP/InGaAs single heterojunction bipolar transistors

Abstract

attention in the recent years because of their use in the high In this paper, we report the effects of high-energy electron irradiation on the DC characteristics of polyimide passivated InPnnGaAs single heterojunction bipolar transistors. In contrast with the results of electron irradiation of unpassivated devices, the polyimide-passivated devices show much less degradation of current gain and no change in the collector output conductance. The decrease of collector current in the active regime is found to be typically -9 percent for a cumulative equivalent I-MeV dose of 2 . 7~1 0 '~ e/cm2 (-620 Mrad (InGaAs)). For low base currents, the devices show an .i -performance lightweight electronic systems in military and commercial space satellites [2-61. We have reported results on electron irradiation effects in unpassivated InPAnGaAs single heterojnnction bipolar transistors (SHBTs) and double heterojunction bipolar transistors (DHBTs) in our earlier studies [5,6]. Our results showed a significant degradation of the transistor performance for irradiation doses greater than 1x10" e/cm2. The degradation effects include a decrease of current gain, an increase in the output conductance and an increase of V C~,~.~, the collector -emitter volvage at which the transistor comes out of saturation. In this oaner, we investigate I I increase in the cnrrent gain for smaller doses (<2.5X1O8' e/Cm') the electron irradiation effects in polyimide passivated followed by a decrease at the higher doses. The increase in the InPAnGaAs SHBTs. Our present studies show that the electron current gain at low doses is attributed to the trapped charge in irradiation induced degradation of polyinlide passivated the polyimide layer near the periphery Of the B-E Junction. The devices is much less than that of the unpassivated devices. Our most significant effect of electron irradiation on the passivated show that the electron energy loss in the polyimide devices is a decrease in the slope of the IC-Vc~ characteristics layer is very low and hence the polyimide layer does not of some devices in the saturation regime. We believe this provide much shield'. we believe that the increased decrease in slope is caused by an increase in the collector series radiation tolerance of the po~yimide-passivated devices is due resistance after irradiation. Finally, devices with smaller to the smaller radiation damage at the peripheries of the baseemitter size are shown to have less radiation degradation than emitter and base-collector junctions as to the the larger emitter devices. This is explained by the smaller unpassivated junctions, radiation damage at the junction peripheries of the passivated devices. EXPERIMENTAL DETAILS

Neutron irradiation effects in InP/InGaAs single heterojunction bipolar transistors

“…Thus, , can be excluded from the further analysis of radiation-induced effects. It should be noted that a similar behavior has been observed in neutron-irradiated AlGaAs/GaAs HBTs [7], and electronirradiated InP/InGaAs [1] and AlGaAs/GaAs devices [8]. The two remaining components of the base current in (5) have been analyzed using the following expressions:…”

“…The thickness and the doping concentration of the various layers in the device structure are summarized in Table I. The devices were fabricated at Oregon State University by a nonself-aligned process using the standard photolithography and selective wet chemical etching techniques as summarized elsewhere [1]. A wafer with four identical test dice, each containing twenty three HBTs of different emitter sizes with areas ranging from to and perimeter/area (P/A) ratios ranging from 0.08 m to 0.4 m , was used for the irradiation experiments.…”

“…Reliable operation of the devices/circuits in such a radiation-harsh environment is of a critical importance and requires thorough investigation of the radiation-induced effects during the product development phase. Radiation tolerance of InP/InGaAs HBTs to electron irradiation have been investigated in [1]. This paper presents the results of our neutron irradiation experiments on InP/InGaAs single heterojunction bipolar transistors.…”

Reliability and Radiation Hardness of Compound Semiconductors

“…The basic reason is that it is not possible to make extremely high-quality insulators (such as Si0 2 ) in compound semiconductor systems. Figure 8 shows how electron damage affects InP/InGaAs heterojunction bipolar transistors [32]. Very little damage occurs until the total dose is above 50 Mrad, even at low current densities.…”

The Study of Deep Level Traps and Their Influence on Current Characteristics of InP/InGaAs Heterostructures

“…The InP/InGaAs material system has the advantages of high electron mobility and large hetero-junction offsets, which promote the realization of InP-based heterojunction bipolar transistors (HBTs) in high-speed analog circuits [1]. In space communication systems, the degradations induced by electron [2], neutron [3] and proton irradiation would cause issues of reliability.…”